Cameron, responding to criticism by Prime Minister Gordon Brown last week that the financial crisis was no time for a novice, told supporters at his party conference that "what matters more than experience is character and judgement".
His Conservatives party's poll lead is still enough to win a majority of about 50 seats if an election were held but there are signs that voters may prefer Brown to be in charge in an economic downturn given his experience as finance minister.
One poll this week showed 43 percent of people felt Brown was best in a crisis, compared with 33 percent for Cameron.
"If we win, we will inherit a huge deficit and an economy in a mess," Cameron, 41, told delegates to the Conservatives' annual meeting in the central English city of Birmingham.
The deepening credit crunch and nationalisation of lender Bradford & Bingley has raised fears of a recession in Britain and boosted support for 57-year-old Brown among voters who say they want an experienced hand at the wheel.
"We will need to do difficult and unpopular things for the long term good of the country. To rebuild our economy, it's not more of the same we need, but change. Experience is what they always say when they try to stop change."
Not Too Complacent
Polls have put the Conservatives ahead of the ruling Labour Party by as much as 20 points this year, suggesting they are on course for an emphatic victory in a parliamentary election due by mid-2010 after 11 years in opposition.
But that lead has halved since Brown's well-received speech to the Labour conference last week which hushed talk that, after just over a year in the top job, Labour needed a new leader to give them any chance of winning a fourth term in power.
Party officials say Cameron, who has repositioned his party at the centre of British politics, is wary of appearing too complacent about an election victory or too partisan in the difficult economic environment.
But his speech contained several pithy attacks on Brown and was full of statesman-like rhetoric as he sought to prevent the conference being overshadowed by the financial upheaval.
"The man is ready for prime minister. He's put fire in my belly," said retired army officer Tex Pemberton, a 69-year-old Conservative activist.
The credit crunch has hit Britain's economy hard this year, forcing the nationalisation of two banks and the private-sector rescue of the country's biggest mortgage lender.
Many economists say Britain is on the verge of its first recession since the early 1990s, making it tough for any government to find room to reduce taxes or increase spending.
"I believe in low taxes," Cameron said. "But we will only cut taxes once it's responsible to do so, once we've made government live within its means."
