Parliament’s attempt to block disclosure of the expenses that MPs claim for their second homes has been thrown out by the High Court in a damning judgment that dismissed the Speaker’s case as unrealistic.

The House of Commons was ordered to pay the full legal costs of its opponents, expected to reach £200,000, as it considers whether to appeal further.

Parliament has been ordered to disclose the details of 14 MPs’ second-home allowances, receipt by receipt, by 4pm next Friday if it is not granted leave to appeal. A decision on whether to try again is likely to be made by MPs on Monday night.

The Speaker, Michael Martin, had to replace his lawyers after they warned him that Parliament would not win this appeal process.

Lord Justice Latham and Mr Justice Blake dismissed Parliament’s attempt to prevent disclosure as wholly unreasonable. In a written judgment, they said: “Once legislation which applies to Parliament has been enacted, MPs cannot and could not reasonably expect to contract out compliance with it, or exempt themselves, or be exempted from its ambit. Such actions would themselves contravene the Bill of Rights.”

The judges also upheld a decision by the Information Tribunal that MPs’ private addresses should be made public as part of the disclosures, arguing that they were “not very private at all”. This is the main reason many MPs wanted to appeal against the judgment and has provoked much anger among those who argued that it would put them and their families in danger.

But the judges pointed out that MPs’ addresses were already disclosed when they sought nomination for election, that company directors had to provide a residential address and that everyone’s full address was recorded in local libraries or town halls. “The reality is that an individual who is determined to discover a residential address of an adult law-abiding citizen is likely to be able to do so by one legal means or another, and where the person concerned is the holder of a public office and in the public eye, such an inquiry is likely to be easier.”

The tribunal had already concluded that MPs could keep their address secret if they had a “special security reason”, for example, “because of a problem with a stalker or a terrorist or other criminal threat”.

The High Court gave the Speaker and his committee until 1pm on Tuesday to decide whether to appeal and to submit outline arguments. An appeal judge must then decide by the end of next week whether the case has any chance of going forward.

If the Speaker decides not to appeal, or the appeal judge throws out Parliament’s latest attempts to block or delay the ruling, then detailed expenses of the 14 MPs, including addresses, must be disclosed by 4pm on Friday.

The 14 include Gordon Brown, David Cameron, Sir Menzies Campbell, George Osborne and John Prescott, as well as Tony Blair, who stood down as an MP last year.

The Information Commissioner, who deals with appeals on freedom of information cases in the first instance, indicated that they would treat this tribunal as setting a significant precedent.

Graham Smith, Deputy Information Commissioner, said: “The High Court ruling brings clarity and will serve as a useful point of reference for the Information Commissioner’s Office in the consideration of future cases under the Freedom of Information Act.”

Heather Brooke, the information rights campaigner who, with The Sunday Times and The Sunday Telegraph, has fought for the disclosure, said: “It is not right that a citizen is forced to fight so hard for such a basic level of democratic accountability from our elected representatives. All the while MPs have used taxpayer’s money to pursue this case through the courts just so they can avoid being accountable to their constituents for how they spend public money. They should be ashamed.”

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