The House of Commons Speaker John Bercow is trying to block the publication of details of MPs' expenses which could show if they are renting their taxpayer-funded homes to each other, it was reported on Thursday.
Bercow has written to the regulator urging it not to release documents revealing the identities of MPs' landlords for security reasons, according to The Daily Telegraph.
The newspaper said disclosure would expose the extent to which MPs are taking advantage of a "loophole" which allows them to rent properties to each other.
It said the concession meant MPs could still build up property nest eggs at the taxpayer's expense, despite moves to stamp out the practice follow the expenses scandal.
However Bercow was said to have written to the Independent Parliamentary Standards Authority (Ipsa) warning that its plan to reveal the identities of MPs' landlords had given rise to "grave concerns" about security.
The Telegraph quoted the letter as saying: "The processing of the data ... could involve causing unwarranted damage and distress. I should be grateful if you and your colleagues would reconsider such a plan."
According to Channel 4's Michael Crick, Ipsa knows of four MPs known to be renting to each other:
Labour MP John Mann said the attempt to prevent the publication of the details appeared to be a "return to the bad old days".
"If MPs are renting from past or current MPs it is right and proper the public is able to know that," he told the paper.
"There is nothing wrong with that, and there is nothing wrong in it being out there in the open. I have no problem in MPs renting it (a flat) out but the public is entitled to know that."
Conservative MP Nadine Dorries joined Mann, saying she would prefer the public not to know where she lives for her own security. She tweeted:
A spokesman for Ipsa told the Telegraph: "We are committed to transparency as is shown by our regular publication of all claims by all MPs. We have a duty to balance that against the risk of compromising security.
"We are currently going through the process of gathering all the relevant information to get that judgment right."
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