Mr Clegg attacked the scale of Conservative plans for more cuts after the Tory chancellor, George Osborne, said the alternative to Conservative fiscal plans was “economic chaos”.
The Lib Dem leader told the BBC’s Andrew Marr Show: “I just think the Conservatives are kidding themselves and seeking to kid British voters if they are claiming that it is possible to balance the books, deliver unfunded tax cuts, shrink the state and support public services in the way that everybody wants.
“It just doesn’t add up.”
He added: “I do think the Conservatives now need to come clean because they are not being straightforward with people.
“How many colleges will be closed, how many primary schools will be closed, how many police will be taken off our streets, how many people who are in the working age poor will be hit by these plans?”
Mr Clegg avoided questions over whether he would back a VAT hike if he was returned to power but said Conservatives “constantly” tell him privately that they support his plans for a mansion tax.
He spoke out after Mr Osborne told the Sunday Times: “It’s hard to work out exactly what they (the Lib Dems) think.
“While they sign up to deficit reduction, they want more tax rises rather than spending cuts.
“But they shouldn’t pretend to people that the sums required can be achieved by their homes tax alone. If you want higher taxes to do the heavy lifting, you’d also need to increase taxes like income tax or national insurance.
“The battle lines for the general election have been drawn this week. There’s a clear choice: a competent plan to stay on course to prosperity with us or a return to economic chaos with all the alternatives.”
Labour’s Chuka Umunna said the coalition was a “heartless and hopeless Government” that is “pulling the rug from under people” with cuts to public services.