Justice secretary Ken Clarke is expected to submit plans to the Treasury today that will slash the £2.1bn legal aid budget by a quarter.

The huge cut of half a billion pounds is a response to chancellor George Osborne’s demands for sweeping cuts to be made across Whitehall departments. Most departments have been told to prepare plans for cuts of up to 25% during this parliament, with further cuts of 40% to be implemented in future.

Departments are understood to be due to submit their opening bids to the Treasury today.

Law Society head of legal aid Richard Miller said: ‘Cuts on this scale are impractical.’

He said it would be more effective to tackle the problems that drive demand from the legal aid scheme, such as lengthy prosecutions.

A spokesman for the Ministry of Justice said the figure of half a billion pounds was 'purely speculative'.