Labour is to blame for too much tax and regulation, Mr Cameron said
Conservative leader David Cameron has told senior City figures his party would offer a new "economic dynamism" to boost business and investment.
He said financial turbulence had shown "serious failures" in the government's economic strategy since 1997.
He said businesses had been stifled by tax and regulation and pledged to simplify the system.
But the government said his plans were "reckless" and he was talking down the economy for short-term political gain.
In a speech in the City of London, Mr Cameron accused the government of "dithering and delay" in the face of the credit crunch and said it had illustrated failures in its policies since 1997.
'No magic pot'
He said the British economic picture was one of "financial turmoil in the foreground and, looming in the background, an inexcusable failure to prepare for difficult economic times".
There was no "magic pot of money," he said, but it was his ambition to "aggressively reduce business taxation" - saying the system could be simplified.
Mr Cameron said he was a "free marketeer" but that did not stop the government helping to create conditions for businesses to invest and thrive in the UK through involvement in transport, research, education and skills.
And he said he wanted a new economic strategy "to attract the best and most productive firms to Britain and keep them here".
Mr Cameron cited problems encountered by pharmaceutical and technology firms in his Witney and West Oxfordshire constituency.
"Witney doesn't have a railway station and is connected to the nearest city, Oxford, by just a single-carriage road," he said.
"Local businesses there don't just need economic stability; they don't just need lower tax and fewer regulations.
"They need the infrastructure, in the broadest sense of the word, to succeed. They need good transport links so they get their goods up and down the country and beyond."
He also set out plans to reform the Bank of England's role to cope with another crisis like Northern Rock - saying it should be in charge of rescuing a failing bank rather than the Financial Services Authority.
And he called for reforms of the Basel accords on international bank regulation.
He said a Conservative government would be "prudent" and "committed to economic stability".
But Business Secretary John Hutton said the Conservatives would cut tax credits and rights at work.
He said: "The only economic strategy David Cameron has is to talk down the British economy for his own short-term political advantage.
"In a climate of global economic uncertainty, the Conservatives' response is billions of pounds of unfunded tax pledges, moves to scrap tax credits for families and cuts to employment rights agreed with Europe - causing years of instability.
"Labour will always put stability first and support Britain's hard-working families."
On Friday a YouGov poll of 1,926 electors across Britain for the Daily Telegraph suggested the Conservatives, with 43%, had a lead of 14 points over Labour.
It put Labour on 29% and the Lib Dems on 17%.