The House of Commons has lost its High Court battle over an information watchdog's decision to force disclosure of MPs' expenses.
The Commons challenged the Information Tribunal's "unlawfully intrusive" demand that a detailed breakdown of MPs' additional costs allowances (ACA) must be provided under the Freedom of Information Act.
The Commons also attempted to overturn the Tribunal's decision that MPs' addresses should be disclosed, arguing they should be kept secret for special security reasons.
But today Sir Igor Judge (President of the Queen's Bench Division), Lord Justice Latham and Mr Justice Blake, ruled at London's High Court that they could not interfere with the Tribunal's decision and dismissed the challenge.
The allowances cover expenditure incurred when an MP is away from home on parliamentary duties. They include the cost of running second homes and general household bills.
They have come under sustained criticism in recent months following the publication of the "John Lewis list" of household items MPs can purchase under their £23,000-a-year second homes allowance.
The list includes £10,000 kitchens and £6,000 bathrooms.
The legal challenge, expected to cost more than £100,000, was instigated by a Commons committee chaired by Speaker Michael Martin.
The ruling was welcomed by pressure group the TaxPayers' Alliance, whose chief executive Matthew Elliott said: "This is a victory for taxpayers and democracy in Britain.
"People have a right to know what their elected representatives are doing and taxpayers deserve to know how their money is being spent. This verdict will boost transparency and bring Parliament closer to the people.
"It's a shame that the Speaker has wasted so much of our money trying to keep this information secret. When he should have been improving the standing of Parliament, he has instead brought it into even greater disrepute by his contempt for the public."
Today's ruling was a victory for journalists and information freedom campaigners Heather Brooke, Ben Leapman and Jonathan Ungoed-Thomas.
Later they welcomed the High Court's ruling that "public money should be, and seen to be, properly spent".
Louis Charalambous, solicitor representing Ms Brooke, said: "Perhaps now the House of Commons will give up its fight to retain antiquated procedures for paying its members' allowances without regard to transparency and the public interest.
"This decision confirms the advance of Freedom of Information law and is a significant victory for our client Heather and the other journalists."
The Information Tribunal ruled in February that the Commons authorities must provide a detailed breakdown of the ACAs of 14 named MPs, including party leaders Gordon Brown, David Cameron and Nick Clegg.
Nigel Giffin QC, appearing for the Commons, argued that the Tribunal's decision, which requires breakdowns to include receipts and the addresses of properties bought, meant there would be "a substantial unlawful intrusion" into the lives of MPs and their families.
Giffin said the Tribunal had taken a legally flawed approach by not giving weight to the "legitimate expectation" of MPs that there would be no detailed breakdown of their expenses, or release of their home addresses, into the public domain.
He stressed the addresses issue was particularly of "considerable concern" to MPs because it raised issues of security.
But the judges ruled that it was in the public interest that there should be full public disclosure.
Ben Leapman, assistant news editor of The Sunday Telegraph, said: "I am delighted by today's verdict.
"The High Court has upheld our view that taxpayers are entitled to know how MPs spend public money on their second homes.
"The Commons should not have spent three years fighting to keep these details secret, at huge cost to the public purse.
"Now MPs need to come up with a regular publication system which will reveal exactly what items they claim for.
"I was the only journalist who requested the publication of MPs' second-home addresses, so I am particularly pleased that the judges agreed with me on this point.
"Most MPs, like ordinary voters, already publish their addresses on the electoral roll.
"As this judgment makes clear, the expenses system has been abused in the past so there is a legitimate public interest in disclosing the addresses for which mortgage or rent is claimed."