Commons Speaker heading a review of MPs' expenses spends £700,000 on his home improvements - and nearly £1m on his garden

More than £100,000 a year has been spent on average on items including furniture, art and air conditioning for the Grade 1-listed apartments.

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Another £992,000 has been spent on Speaker's garden, although most of the costs have gone on improving security since 9/11.

The figures were released to the Daily Telegraph under the Freedom of Information Act and come as the Speaker is under intense pressure over MPs' expenses.

They show that £148,900 has been spent on furniture, £191,000 on a new air-conditioning system, £13,000 on art and £291,000 on "building restoration and refurbishment" in Speaker's House.

In total, £724,000 has been spent on the residence - which also includes the State Rooms of the Palace of Westminster - since 2001. With the money spent on the garden, the total jumps to nearly £1.7million.

Mr Martin was elected Speaker in October 2000.

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Security costs for the Palace as a whole have escalated since 2001.

Former independent MP Martin Bell, the anti-sleaze campaigner, said he was "shocked".

"The Speaker should be setting a good example and he is not - MPs have got to get their palace in order," he said.

"We are close to a state of constitutional crisis. You run out of words in the end to describe his behaviour."

Mark Wallace, campaign director of the TaxPayers' Alliance, said the disclosure proved that Mr Martin was the wrong person to be heading a review of MPs' expenses.

He said: "These are stupendous sums to spend on just one residence. The Speaker is well paid and receives generous allowances as well as a free house, so it is excessive for him to be billing so heavily for furniture, art and cooling systems."

Mr Martin's spokeswoman said the spending was part of a rolling programme of improvements which were commissioned by the Parliamentary Estates Directorate.

She stressed that the House included more than just Mr Martin's grace and favour apartment.

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She said: "Speaker's House is the official residence of the Speaker. Entertainment of visiting heads of state, Parliamentarians and others take place in the State Apartments and the costs listed reflect environmental and heritage requirements and health and safety legislation."

The Speaker has already come under fire for claiming more than £75,000 of second homes allowance on his Glasgow property, for which he has no mortgage.

His wife has claimed thousands of pounds in expenses for taxis, the disclosure of which led to a row which caused Mr Martin's previous spokesperson, Mike Granatt, to quit.

In the last week, the House of Commons Commission - which the Speaker chairs - has faced criticism from MPs for launching a High Court appeal against the release of a detailed breakdown of MPs' second home claims.