Tax campaigners attack MPs who refuse to reveal how they spend £11.8m housing perk

Despite pledges for greater transparency on expenses from the main party leaders, MPs are stubbornly fighting an order to publish detailed breakdowns of their allowances to run second homes.

Critics said the refusal, spearheaded by Commons Speaker Michael Martin - who this week set up a review of MPs' expenses - was a "squalid" bid to shroud taxpayer-funded Parliamentary allowances in secrecy.

Corin Taylor of the TaxPayers' Alliance said: "It is shameful hypocrisy for MPs to behave in this way.

"It is a sad state of affairs that on one hand they say they will be more open about spending public money, while doing everything in their power to keep it secret."

Freedom of Information campaigners are pressing the House of Commons authorities to release receipts showing in detail how each MP spends his or her £22,110-a-year additional costs allowance.

But the Commons Commission, chaired by Speaker Martin, has refused to release the information on the grounds that it is an invasion of privacy.

Today an Information Tribunal panel will begin a twoday hearing on the dispute, which has been running for four years.

The result may not be released for several weeks and could result in a further appeal to the High Court.

Gordon Brown, David Cameron and Nick Clegg have all urged MPs to come clean about their office and housing allowances in the wake of the Derek Conway scandal. The Tory backbencher paid his sons £75,000 of public money to do research for him even though they were full-time university students.

The outcry led to Speaker Martin promising to review MPs' perks in a bid to ensure "transparency".

But despite the promise of a new era of openness, the Commons Commission has refused to back down in its attempt to keep details about MPs' second homes allowances secret.

Heather Brooke, of anti-secrecy campaign group Your Right To Know, who first requested the information, said: "Disclosure of MPs' expenses in a manner that allows scrutiny is in the public interest and necessary for open government.

The current annual-breakdown by categoriesis useless in terms of holding MPs to account. None of the current abuses of MPs' expenses can be seen in such bulk figures.

"It isn't right that the only way the public can uncover the detail necessary to ensure against corruption is through leaks, gossip and rumour."

But Nick Harvey, a Libem member of the Commons Commission, said: "If the public wants to know about our office, travel and staff costs that's perfectly legitimate, but what goes on behind our personal front doors is our business.

"If we're going to get to the state where local press or political opponents complain because we spent £25 on a kettle when Argos does them for £6, or we bought curtains from John Lewis when you can get them for less at the Co-op, then they can get lost.

"It's no business of the public what we spend on our own homes."