The Deputy Prime Minister said Liberal Democrats would raise taxes to help fill the black hole in public finances while the Conservatives would try to balance the books by “beating up on the poor”.
It comes after he urged his “underdog” party to fight “tooth and nail” to prevent a Conservative or Labour majority.
Mr Clegg insisted that his party would block any attempts to take Britain out of the European Convention on Human Rights - a move floated last week by Conservatives.
But he refused to rule out bringing down the cap on welfare payments from £26,000 to £23,000 set out by the Conservatives last week.
In an interview on BBC1’s Andrew Marr Show on Sunday morning he accused the Conservatives of announcing with “almost undisguised relish” that they would not ask the wealthiest to pay a “single penny towards completing the deficit reduction effort”.
The Lib Dem leader said that trying to clear the deficit without raising taxes was “economically extreme”.
Asked if the Lib Dems would raise taxes, he said: “Yes, of course. We must raise taxes.”
Mr Clegg said changes to tax relief for the wealthiest pensioners and extending council tax bands to the most expensive properties were among the tax reforms proposed by the Lib Dems that would help fill the deficit black hole.
He added: “What we are saying is that those choices, either sticking your head in the sand or beating up on the poor, are not the choices the British people want. They want balance. They want balance between a strong economy and a fairer society and that is what we are offering.”
Asked why the Lib Dems remained in government with a party they despised, he replied: “We have restrained the Conservatives from doing what they want on penalising the poor, on ignoring the environment, on trashing our civil liberties and human rights.”
Pressed on whether Mr Clegg would stop the Tories reforming the cap on welfare claims in a future government, Mr Clegg said he would look at any proposals.
“I’m very happy to look at things like that but I do not believe that ratcheting down the welfare cap is the answer. It’s certainly not something we are advocating.”