Bold and even "savage" cuts in government spending will be necessary to bring the public deficit down after the next election, Nick Clegg, the Liberal Democrat leader, says today.

As the three main parties begin the conference season with competing proposals for how they would make spending cuts, Clegg used a Guardian interview to set out plans including a long-term freeze in the public sector pay bill, scaling back future public sector pensions, and withdrawing tax credits from the middle class. He is even prepared to examine means-testing universal child benefits, though he is cautious of destroying "middle-class solidarity" with the welfare state.

"I find it odd that people on multi-million pay packages from the city get child benefit. That's patently silly and patently unfair," he says.

Clegg predicts that voters will show Gordon Brown the exit at the general election, and pleads with Labour not to hold a referendum on electoral reform on the same day, saying it will set back the case by 20 years. "Anything that Gordon Brown proposes now will turn to dust," he says.

The Liberal Democrats also attacked Tory spending plans last night, claiming that Treasury documents released under the Freedom of Information laws revealed £53bn of unfunded Tory promises. "The Tories try to talk tough on spending cuts, but in reality they haven't a clue," said a spokesman, Lord Oakeshott. "With over £50bn of uncosted spending commitments, they are not fit for government."