The Commons has launched a last-ditch bid to block publication of detailed expenses of 14 MPs and ex MPs including Gordon Brown and David Cameron.
The expenses relate to claims by MPs to furnish a second home
The Commons authorities had been expected to release details of second home expenses later on Tuesday after a Freedom of Information tribunal ruling.
But they have launched an appeal against the ruling on the grounds it could compromise MPs' security.
The FOI ruling last month follows a three year battle to stop publication.
The Commons authorities had until 1600 GMT on Thursday to launch an appeal, which they have now done.
Explaining the decision, a Commons spokeswoman said: "The threats that MPs can face are unpredictable and subject to change."
The release of their home addresses could "inhibit democratic debate" on a range of sensitive issues, she added.
The Speaker is said to have been "mindful" of MPs' concerns and has sought advice from the security services.
"Having received advice he's concerned that the Information Tribunal may have misdirected itself in law in deciding that home addresses of MPs should always be published subject to only to limited exceptions," the spokeswoman said.
The Commons also considers that the tribunal gave "insufficient attention to the reasonable expectations" of MPs.
No information will now be made public until the case is heard at the High Court.
The Commons authorities - which include the Speaker and senior MPs from all the main parties - have spent years fighting calls to account for public money spent on expenses by MPs.
The FOI tribunal ordered the publication of a detailed breakdown of what the 14 MPs and former MPs claimed over three years.
If the details are published, the public will be able to see what politicians such as Gordon Brown, former Prime Minister Tony Blair and former Deputy Prime Minister John Prescott spent on everything from their mortgage to soft furnishings on their second home in London.
The figures for Conservative leader Mr Cameron, shadow chancellor George Osborne, shadow foreign secretary William Hague and former Lib Dem leader Sir Menzies Campbell are also included in the case.
'John Lewis list'
Earlier this month it emerged that MPs were allowed to claim expenses of up to £10,000 for a new kitchen, £2,000 for furniture and £750 for a TV or stereo for their second homes.
And other claims allowable include £6,335 for a new bathroom, £299.99 for air conditioning units, £300 per rug, £50 for a shredder and £1,000 for a bed.
The figures are in the so-called "John Lewis list" used by Commons officials to list maximum amounts for items.
The existence of the list - based on prices at the John Lewis store "because it was highly rated by Which magazine" - was revealed during the tribunal.
The Commons authorities are also refusing to release the details of expenses claims by six MPs included in a 2005 Freedom of Information request by the BBC.
The Information Commissioner ruled against the BBC's request for "full information" on the six then MPs - Tony Blair, John Prescott, Gordon Brown, Michael Howard, Charles Kennedy and Jonathan Sayeed - between April 2003 and March 2004 for reasons of personal privacy.
But he decided that the Commons should release details of travel expenses, staffing, IT provision, stationery, incidental expenses and the total amount claimed by the named MPs under the Additional Cost Allowance over the period.
The Commons authorities initially said they would comply with the ruling but then said they had decided to appeal against it.