The Liberal Democrat leader and his deputy Vince Cable will launch their manifesto this morning.
They are expected to announce a range of measures, including plans to tackle bank bonuses and reform the tax system.
Due to be unveiled at the Bloomberg building in the City of London, the manifesto is built around "four steps to a fairer Britain".
These include "fair taxes" such as raising the the income tax threshold to 10,000 pounds, reforming the education system by reducing class sizes, economic reform including breaking up the big banks and wide ranging constitutional change including giving voters the power to sack corrupt MPs, reform of the voting system, an elected House of Lords and a Freedom Bill to restore civil liberties.
In the forward to the manifesto Clegg says the Lib Dems will "sort out our rotten political system once and for all".
He writes: "Elections that can really make a difference don't come along very often. But this is one of them.
"This May, you have an opportunity to shape the future of our country for the better.
"We've had 65 years of Labour and the Conservatives: the same parties taking turns and making the same mistakes, letting you down.
"They have taught people to expect little from politics, and get less.
Questions about how the party will act in the event of a hung Parliament are likely to persist after a poll published in today's Times suggests the Conservative lead has narrowed to just three points.
A Populus poll for the paper put the Conservatives on 36 per cent, Labour on 33 per cent and the Liberal Democrats on 21 per cent.
And a ComRes poll for The Independent and ITV News also appears to show the race is narrowing after one week of campaigning.
The survey puts the Tories on 36 per cent, Labour on 31 per cent and the Liberal Democrats on 19 per cent.
