An MP who led criticism of Parliamentary expenses has admitted claiming about £20,000 from the taxpayer to rent an office he already owned.

Norman Baker, Liberal Democrat MP for Lewes, claimed the cash to rent a constituency office in the building he had bought as his own home.

The 51-year-old has become a regular “talking head” on news programmes in recent days and repeatedly condemned the extravagant expenses claims which have outraged the nation this week.

His political opponents last night branded him a hypocrite after details emerged of his arrangement to claim money to rent the office space at the house he owned in High Street, Lewes.

Mr Baker said yesterday he had checked he was not breaking any rules before buying the house and making the claims.

He said he had claimed roughly £7,500 a year for about three years after buying the house for £310,000 in September 2000.

He told The Argus: “I was entitled to claim money from the taxpayer for the rent of an office to carry out my parliamentary office.”

Mr Baker said he stopped making the claims and went without the cash for another two years before moving his office to East Street.

He said he could have made money by renting the office out commercially and argued he had saved the taxpayer money by stopping his claims while leaving himself “thousands of pounds out of pocket”.

Mr Baker said: “The taxpayer has paid no extra money whatsoever as a consequence of that arrangement.

“The taxpayer has saved a good deal of money

“The taxpayer is in the black. I am in the red.”

Julian Lewis, a Conservative MP who crossed swords with Mr Baker when the Liberal made comments to a national newspaper in a story about Mr Lewis's expenses claims, said: “It is utter hypocrisy.”

Jason Sugarman, Conservative parliamentary candidate for Lewes, said: “We need to clean up politics and that means everybody needs to be transparent and clear.

“He is tarred with the same brush as the MPs he criticises.”

In The Daily Telegraph, which has published fresh revelations about MPs' claims every day since last week, Mr Baker was yesterday reported to have had claims turned down for a bicycle and a computer at the London home he rents.

He also claimed hundreds of pounds for food in periods when the House of Commons was not sitting.

He told The Argus: “It is standard practice right across business that when you're away from your home you claim subsistence.”

Mr Baker said he had claimed far less than the maximum he would have been allowed.

He said a request to claim for a computer so he could listen to music and email his family was filed sarcastically after his initial claim for a computer for work reasons was turned down.

Mr Baker was a champion of the parliamentary campaign to release details of MPs' expenses claims under the Freedom of Information Act.

He has become a prominent critic of the Government and wrote a book about the death of civil servant David Kelly, as well as campaigning locally on issues like the Newhaven incinerator.

Since the Telegraph’s revelations began, he has led the chorus of disapproval at outrageous claims by MPs.

In the House of Commons this week he was condemned by the Speaker for asking if the publication of MPs' expenses could be brought forward.

The Speaker, Michael Martin, said: “You are another individual Member who is keen to say to the press whatever the press wants to hear.

“It is wrong for the honourable gentleman to have said that the House of Commons Commission has done nothing.”

Mr Baker himself branded the Speaker's stance “disgraceful” after Mr Martin criticised people calling for greater transparency.

He wrote in a national newspaper on Monday: “The basic problem is this: claims for expenses should reflect expenditure legitimately and necessarily incurred by a Member of Parliament as part of his or her duties – no more, no less.

“Instead, they have been used by too many MPs as an alternative income stream, as a way of bumping up salary without having to vote through an embarrassing increase.

“The standard defence trotted out is that everything done has been within the rules. But that does not make it ethically correct, not least because those rules have been written by MPs themselves.”