The earl has made a series of claims about the King in his new book - alleging he said "we'll forget her soon enough" during a row over funeral arrangements for his sister Princess Diana.
Buckingham Palace said in response that "fraternal grief can cloud reason, affect judgment and colour memory in ways others do not recognise".
The earl has stood by his comments in several interviews, in which he also likened the media's treatment of Prince Harry and Meghan to what Diana went through.
In his BBC interview, Earl Spencer also claimed:
- He knows "lots of facts about the King" that he did not put in the book as he's not a "salacious writer". He denies that's a threat.
- He won't go into what he's said to William and Harry, but says his "words will not be a surprise to them".
- Alleges the King "went ballistic" and "ranted" when challenged over Diana's sons walking behind her coffin.
- In the same conversation, claims he hung up on Charles after he allegedly said "we'll forget her [Diana] soon enough".
- His eulogy to Diana - that her "fantastic qualities will never be extinguished from our minds" - was a "direct rebuttal".
- He doesn't know "finer detail" of her sons' rift, but "a mother would want her two sons to be happy together and love each other".
- The earl worries about Harry not having police protection in the UK.
In an interview in The Mail on Sunday, Earl Spencer hit out at the Palace's response to his claims, telling the paper: "It is not every day you wake up to find you've been gaslit by the King.
"It was astonishingly provocative and below the belt because it was essentially trying to say I'd lied without the King being able to deny what I'd said.
"I also thought it was a rather poor imitation of the 'recollections may vary' quote, which was a much more elegant way of putting things, but in these circumstances entirely out of place."
He also said Diana "would be cheering from the rafters at this book".
The earl made the allegations in Swan Song: Diana, My Sister, which is being serialised in the Daily Mail and is due to be published next week.
Harry and Meghan 'being destroyed daily'
In his BBC interview, the earl was asked if he thought Diana would "identify" with how Prince Harry and Meghan have been treated by the media.
"If you look at an article in a tabloid about Diana or the couple that you were mentioning, Harry and Meghan, you know, they can be really, really unpleasant," he told the BBC.
"And I think it would be really beholden on people to learn from Diana's example."
The earl added: "I'm not here to speak for Harry and Meghan, but for anyone who's being destroyed in this way daily, it must be such a cancerous influence in their life."
He said Diana was "really brought low" by her treatment by the media, and it was a "pity" to see "echoes of that" in the coverage of Prince Harry and his wife.
The earl has insisted he is telling the truth about the King and accurately remembers what was said at the time.
He told the BBC: "I told friends and family straight away, close friends and family, about what had been said, because it was so monstrous."
The King allegedly made the remarks about forgetting Diana during a row over whether William and Harry should follow the funeral cortege.
Earl Spencer walked behind Diana's coffin alongside her sons, Charles, and the late Duke of Edinburgh.
The earl said his book is his "final word and celebration" of Diana and he's now "done" with speaking publicly about that time.
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Despite intense coverage of the earl's claims, the Royal Family has been carrying on as usual.
On Saturday, Camilla was at Chatsworth House in Derbyshire for a festival for The Queen's Reading Room, a charity she founded after the success of her book club during the pandemic.
The Queen told people books have a "life-enhancing power" and being at Chatsworth, which has a library of over 17,000 books, was "like coming home".
Exit polls indicated that Mr Merz's centre-right Christian Democratic Union (CDU) came in with just 5% in the northeastern state of Mecklenburg-Western Pomerania - the party's lowest result in any state since the Second World War.
Heavy losses are also expected in Berlin, where the CDU is projected to come in second with 20%, behind the Left party at 24.5%, according to the exit poll.
The far-right Alternative for Germany (AfD) party is predicted to have made significant gains in both elections - 37% of the vote in Mecklenburg-Western Pomerania and 15.7% in Berlin.
Despite predicted gains, it is unlikely to be able to form a regional government.
The votes came two weeks after AfD won the regional election in the small eastern state of Saxony-Anhalt, increasing pressure further on the German chancellor.
Mr Merz struck a defiant note in a statement shortly after the exit polls were announced, rejecting any retreat from his government's reform agenda.
He argued that Germany's economic and political problems made difficult and potentially unpopular reforms more urgent, not less, and pledged to press ahead.
"What needs to be done now requires backbone, steadfastness, and patience," he said, adding that "I will demonstrate these qualities as chairman of the CDU and, above all, as chancellor of our country".
A chancellor under fire
Mr Merz, 70, only became Germany's leader 16 months ago - with promises to turn around an economy that has barely grown in years - but has failed to lift a sullen national mood and has himself become deeply unpopular.
The strong showing of AfD in the Saxony-Anhalt election has further weakened the chancellor's national standing.
In the past two weeks there have been calls even from within his own party to replace him as chancellor, although no top-level allies have called publicly for his departure, and many have warned against "personnel debates".
Apparently anticipating a tough post-election period, the chancellor has abandoned a planned trip to New York next week to attend the UN General Assembly.
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Philipp Amthor, a prominent CDU figure from Mecklenburg-Western Pomerania who now manages relations between the federal and state governments at the chancellery, said on Sunday night that one problem in the campaign had been "the difficult personnel discussions" of recent weeks - an apparent reference to the speculation about Mr Merz's future.
"It is good and right for these personnel discussions not to be continued now," he said.
However, speaking after the exit polls, AfD's national co-leader, Tino Chrupalla, told ZDF television that "the chancellor's statement today really was more than feeble. He announced that he'd carry on as before, instead of finally drawing the consequences and resigning".
Iran's central military command said in a statement on Sunday that Tehran had received information that the United States was planning to resume action, with the backing of some other countries in the region.
According to Iranian state media, the country's military said any US attack will trigger sustained strikes on US bases and interests in the region.
Iran also warned that regional countries supporting any aggression from the United States would be considered parties to the conflict.
The conflict began in late February after US-Israeli strikes on Iran. A 60-day memorandum of understanding brought an end to the strikes in June, but that expired last month, and there have been tit-for-tat exchanges since.
Strait of Hormuz to remain closed, says Iran
It comes after the semi-official Fars news agency reported Iran's parliament speaker has insisted the Strait of Hormuz will not reopen until Tehran's conditions are met.
Mohammad Bagher Ghalibaf said earlier on Sunday that Iran must both fight and negotiate, stating Tehran would use both military force and diplomacy.
The strait remains a key sticking point for peace negotiations.
The US, which is blocking Iranian ports, has often claimed to have seized control of the waterway and insisted it is open.
But it is still largely cut off, and the impact is being seen on fuel prices - with the cost of oil topping $100 a barrel again earlier this month.
Countries condemn Houthi attack on Riyadh
Elsewhere in the region, Egypt, Jordan and Kuwait have said a Houthi attack on the Saudi capital was a violation of international law and a regional security threat.
A pillar of black smoke was seen rising near Riyadh's main airport on Saturday after missile and drone strikes that have since been claimed by the Iran-backed group.
Saudi Arabia said the attack was intercepted and there were no reports of casualties or damage.
In separate statements, Egypt, Jordan and Kuwait said they condemned the attack, as did the Muslim World League, an independent, international organisation comprised of members from various Islamic countries.
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Two killed in the West Bank
A 30-year-old Israeli man has been shot in the West Bank, hours before the Yom Kippur holiday, widely considered the holiest day in the Jewish calendar.
Israeli military said the suspected attacker opened fire from a vehicle and fled on foot. It said he was injured while fleeing and later detained at a hospital where he had sought care.
Separately, the military said it killed a Palestinian man who attempted to ram a car into soldiers in the West Bank, less than an hour later. It said it was still searching for another man who was in the vehicle.
In Iraq, six French nationals have stood trial on suspicion of being members of the Islamic State group, Iraqi officials have told the Associated Press.
Speaking anonymously, the officials said it could take several proceedings before a verdict is issued.
Writing on his Truth Social platform, the US president said he had agreed to the move following a "strong request" from the military.
He also cited national security concerns but did not mention any specific threats.
It echoes the rationale he cited for the $400m (£298m) ballroom complex being built on the site of the White House's former East Wing that has been demolished to make way for the project.
His post on Sunday marked a significant change in the arch plans that had already been in progress, as the Trump administration had announced earlier this month that it was preparing to break ground in the coming weeks.
The arch was set to feature a towering winged figure, flanked by two eagles, and guarded by four lions, all gilded with gold.
The design would also carry the words "One Nation Under God" and "Liberty and Justice for All" inscribed in gold atop either side.
From its base to the top of the winged figure, it would dwarf the nearby Lincoln Memorial, which is 30m (99ft) tall.
The arch, which Mr Trump plans to build between the memorial and Arlington National Cemetery, is part of his efforts to change some of the capital's sites and leave a lasting imprint.
They include the White House ballroom, renaming and renovating the Kennedy Center, refurbishing the Lincoln Memorial reflecting pool and rebuilding a golf course in East Potomac Park that could significantly cut down the public's access to running and biking paths.
The president wrote on Truth Social on Sunday: "At the strong request of the United States Military, and for National Security purposes, I have agreed to convert the magnificent Triumphal Arch, planned since the Civil War Era many years ago, at the Receptive Circle adjoining the Arlington Memorial Bridge, into a top grade Military Complex/Triumphal Arch, to house, store, and have the rapid ability to use large numbers of drones, plus Snipers, on both the roof and plaza areas, and additionally have and hold large quantities of sniper ammunition in storage.
"There will be no facility like this anywhere in the World."
Aviation experts have raised safety concerns given its proximity to Reagan Washington National Airport.
And military veterans have launched legal action to block the arch from being built, arguing it would spoil the historic sightline between the Lincoln Memorial and Arlington National Cemetery, and it needs to be approved by Congress.
The project has not yet received final approval from the National Capital Area Planning Commission, which greenlit the site and preliminary plans at a meeting in July.
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Asked to comment on the president's latest remarks, a Pentagon spokesperson said the department has "nothing additional to provide beyond the post".
The White House declined to provide additional information.
Mother-of-three Joanne Sheen had not been seen since she travelled from Fareham, Hampshire, heading to her home city of Southampton, in December 2019.
The Metropolitan Police were called on 12 August this year after bones, believed to belong to a woman aged 25 to 45, were found near Padstow Walk in Feltham, southwest London, after the area was affected by a blaze.
Detectives had launched a murder inquiry, but Hampshire and Isle of Wight Constabulary has taken over the investigation after the remains were identified as those of Ms Sheen.
A 56-year-old man from Southampton was arrested on suspicion of conspiracy to commit murder and has been bailed with conditions, pending further enquiries.
Police have now confirmed a second 56-year-old man from Southampton was re-arrested on suspicion of conspiracy to murder and was further arrested on suspicion of murder. He has been bailed with conditions, pending further enquiries.
Both men were detained on Thursday 17 September.
Detective Chief Inspector Toby Elcock said the identification of Ms Sheen's remains was a "significant development" in a "long and complex investigation".
More than 4,000 lines of inquiry have been raised and over 300 statements taken, with detailed searches carried out at more than 10 addresses and on numerous vessels, police say.
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A Metropolitan Police spokesman said the remains were found by a member of the public after the nearby land was affected by a recent wildfire.
The site is close to Bedfont Lakes Country Park.
Shrubbery appeared to have been burned in a woodland area close to where the police crime scene was in place last month, and a large patch of the ground was charred.
An incident log on The London Fire Brigade's website showed four fire engines and about 25 firefighters had tackled a grass fire in the area on August 5.
About two hectares of shrubland were damaged in the blaze.