The Speaker is to stand down next month
Michael Martin was pressured by "very senior political sources" into fighting a legal battle to keep MPs' expenses secret, a senior Labour MP claims.
Sir Stuart Bell said the Commons Speaker had been put under "severe pressure" to fight Freedom of Information requests.
The doomed High Court battle is reported to have cost £150,000.
Commons leader Harriet Harman said an "authoritative" legal ruling was needed but denied Mr Martin was "leaned on".
Mr Martin, who recently became the first Commons Speaker in 300 years to be forced from office, unsuccessfully contested an Information Tribunal ruling ordering full details of MPs' expenses to be published.
The Commons Members Estimates Committee, chaired by Mr Martin, gave up its High Court battle just over a year ago, after deciding not to seek leave to appeal.
The information it had fought to keep out of the public domain has formed the basis of a string of revelations about MPs' expenses in the Daily Telegraph.
The information was due to be published by the Commons authorities in July, but with addresses and other details removed, which the newspaper claims would have prevented serious abuses of the system coming to light.
The four-year legal battle to prevent publication was cited by Mr Martin's opponents as one of the reasons why he had to go.
But Sir Stuart Bell, a friend of the Speaker who sits on the influential House of Commons Commission, said he had been under pressure from all sides.
In an interview with BBC Radio 4's
to be broadcast at 2000 BST on Thursday, Sir Stuart said: "The Speaker, unfortunately for him, was caught in this terrible dilemma of trying to meet the requests of the Freedom of Information Act and at the same time trying to say to MPs 'I'm trying to look after your interests'.
"This man, this Speaker of the House of Commons, actually failed because he was trying to help his Members of Parliament.
"The Speaker came under severe pressure from very senior political sources that he must appeal this to the High Court."
Challenged about Sir Stuart's claims, Ms Harman, who is deputy Labour leader as well as Commons leader, told the programme: "I think that it was important that we had an authoritative ruling, a High Court interpretation of what the law was, but also that we were absolutely clear that we were protecting personal addresses."
She added: "When you are the Speaker of the House of Commons you are not leant on by anybody.
"You are authoritative, you are in the position of Speaker and you make your own decisions."
Mr Martin is due to stand down on 21 June. A secret ballot of MPs the following day will decide his successor.
Mr Martin told MPs he was standing down to maintain Commons "unity".
The Report is broadcast on BBC Radio 4, Thursday 28 May at 2000 BST. You can also listen via the BBC
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