The Conservatives and Liberal Democrats are calling for a simplification of the tax system.

The Tories want to create a new body that would regularly consider existing direct tax legislation, and would aim to modify unnecessarily complex provisions.

The Liberal Democrats are also calling for a new commission on tax simplification to be set up, and are drawing up a target list of relief and credits to be reviewed by their proposed commission.

"We think the tax system is over-complicated and changes too frequently," said George Osborne, shadow chief secretary to the Treasury.

"There is too much tax legislation which is a burden on taxpayers and businesses."

Vince Cable, the Lib Dem Treasury spokesman and a former chief economist of Shell, said many of Gordon Brown's tax changes "carry a large deadweight value but don't create much incentive" for businesses to change the way they operated.