A Conservative government could "wipe the slate clean" and help promote economic recovery, party leader David Cameron has said.
A change of administration could "help with confidence", which would encourage investment, he added.
Mr Cameron told BBC One's Andrew Marr Show that the party was "campaign ready", should Gordon Brown call a general election soon.
But Labour said the Tory leader should "come clean" over spending "cuts".
In the interview, carried out in his west London home, Mr Cameron admitted making mistakes.
He said: "I now see just how unaffordable Labour's spending plans are. Perhaps we could have seen that earlier."
Mr Cameron said he would increase government spending from £620bn this year to £645bn next year - rather than the £650bn proposed by ministers.
His proposals are economic madness
Yvette Cooper, Treasury minister
He warned voters not to expect an incoming Tory administration to slash public spending and cut taxes, saying: "That's not what they should be thinking.
"They should be thinking this would be a responsible government that would make government live within its means, that would relieve some of the debt burden being piled up on our children."
For the government, Chief Secretary to the Treasury Yvette Cooper said: "David Cameron still can't tell people what he would cut during a recession.
"His proposals are economic madness - cutting training budgets, housing and transport investment plans and help for people to get jobs just at a time when they need it most.
"He wants to cut £5bn in just three months' time but all he can point to is ID cards and the advertising budget - but he has already committed to spending that money before."
She added: "Cameron should come clean on where his cuts to support for jobs and the economy now will fall."
There has been speculation that the Mr Brown will call an election during the first half of this year, but the prime minister has insisted this is the last thing on his mind.
Mr Cameron said: "We have the money raised, or we're in the process of raising it. We have the campaign ready.
"But the real reason I want it is, I think the key ingredient missing in the economy is confidence - that confidence people have to go out and invest in a business or buy a new home or return to the economy.
"And I think a new government would help with confidence. Why? Because you can wipe the slate clean. You can take long-term decisions rather than short ones.
"You can admit to the mistakes that have been made in the past. You can reshape the regulatory systems that have failed.
"This government finds those things very, very difficult to do. They won't admit to mistakes. The prime minister in particular finds it impossible."
'Very good team'
Mr Cameron said today the Conservatives were doing better now than for three decades but insisted he still did not take the electorate for granted.
Asked about an expected reshuffle of his shadow cabinet, he said: "I've got a very good team. I think they've delivered the best results for the Conservative Party in 30 years."
He added that he always looked at "ways of improving" his team.
On former chancellor Ken Clarke, who has been tipped for a shadow cabinet job, Mr Cameron said: "As far as I'm concerned he's back already."
Asked about David Davis, who quit as shadow home secretary last year to fight a by-election over 42-day pre-charge detention for terror suspects, the Tory leader said: "You will have to wait and see."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.