In an article for The Telegraph, the Prime Minister wrote: "I know that the familiar excuses - low turnout, midterm blues - aren't enough.
"Even the difficulties of our economic situation and the tough but necessary decisions the Government has had to take cannot fully explain the results."
More than 400 Tories lost their seats in last Thursday's local council elections, while 330 from Coalition partners the Liberal Democrats found themselves cast out.
Labour gained 824 seats and won control over an additional 32 authorities.
The Coalition, which marks its two year anniversary this week, will be hoping to get things back on track when it sets out its legislative agenda for the coming political year in the Queen's Speech on Wednesday.
But before that Mr Cameron will stage a joint visit with Deputy Prime Minister Nick Clegg to drive home the message that the Government is focusing on "jobs, growth and the economy".
Mr Cameron said in the Telegraph that voters wanted to know the Coalition was "not just a bunch of accountants".
"When people think about the economy they don't see it through the dry numbers of the deficit figures, trade balances or inflation forecasts - but instead the things that make the difference between a life that's worth living and a daily grind that drags them down," he said.
Tory leaders have been forced to defend themselves after a backlash from the party's MPs and peers after the thumping they received in the polls.
Chancellor George Osborne admitted the results were "tough" but said ministers would continue to take unpopular decisions for the good of the country.