Liberal Democrat leader Nick Clegg tonight said he would offer a "manifesto you can trust" as he dismissed David Cameron's plans for government.
The Tory leader launched his policy programme today but Mr Clegg described it as a "manifesto of style over substance".
The Lib Dem leader said he was determined to offer "something different" to the British people at the General Election on May 6.
The Lib Dem manifesto - published tomorrow - will contain "concrete, specific steps" instead of the "vague aspirational talk" offered by Labour and the Tories, Mr Clegg said.
Mr Clegg seized upon the Tory decision to launch their manifesto at south London's disused Battersea Power Station.
Speaking at a campaign tour event in Bradford he said: "You can't trust the Conservatives.
"They have just launched a manifesto in a power station that doesn't generate power. It's a manifesto of style over substance.
"You can't trust the Conservatives when they want to give tax breaks to double millionaires not tax breaks to everybody else.
"You can't trust the Conservatives when they don't want to clamp down on the bonuses of greedy bankers.
"You can't trust the Conservatives when they don't really want to clean out the corrupt state of politics in Westminster.
"That's why I think we need something different."
Mr Clegg continued: "David Cameron seems to think that it's just his turn to govern, that he should just inherit power rather than earn it."
Asked whether Mr Cameron's manifesto made Lib Dem support for a Tory administration in the event of a hung parliament less likely, Mr Clegg said: "It makes me more determined to offer something different to the British people."
The Lib Dems will produce "a manifesto that you can trust, a manifesto that you can believe in".
He added: "We are not going to promise something for nothing, which is what we've had now from Labour yesterday and the Conservatives today.
"That will be one big difference between the Liberal Democrats and the other two old parties."
Mr Clegg continued his attack during a visit to a factory in Luton, saying the Tories "won't get tough on their friends in the banks in the City of London".
He added: "It's very difficult to believe in their promise of change when I don't believe they have changed very much at all."
Deputy Lib Dem leader Vince Cable joined Mr Clegg on his campaign battlebus for the first time and the pair were taken on a tour of Printing Roller Services, a small firm in Bradford which has struggled to get access to credit.
Speaking to party supporters outside the company Mr Clegg said: "This is a good local company that has not been able to get a loan at reasonable rates from banks we own."
Mr Clegg has called for lending agreements to be properly enforced so the part-nationalised banks provide funds for business.
The campaign entourage later headed south to Luton to visit 2K Manufacturing, a firm recycling plastics into a green alternative to plywood.
Mr Clegg was joined by prospective parliamentary candidate Qurban Hussain, who will be taking on rivals including TV personality Esther Rantzen in the battle for the Luton South seat.
Earlier today, Mr Clegg unveiled plans to crack down on "obscene" bankers' bonuses, warning there would be "no reward for failure".
He said he wanted to see a change in the City of London "as fundamental as the Big Bang of the 1980s".
Under the Liberal Democrats, all bonuses of more than £2,500 would have to be paid in shares and there would be no bonuses at all at board level.
Any loss-making financial institution would not be allowed to pay discretionary bonuses.
And the names of all bank staff whose pay and bonuses are greater than the Prime Minister's salary - just under £200,000 - would be published.