Details of MPs' expenses payments which could show if they are renting taxpayer-funded homes to one another were at the centre of a political row last night after the Speaker of the House of Commons reportedly attempted to block their publication.

Pressured to reveal politicians using the "loophole" in rules introduced following the 2009 parliamentary expenses scandal, John Bercow claimed that doing so would pose a security risk.

Regulations introduced after a review of expenses rules attempted to clamp down on the practice, banning MPs from renting their subsidised properties from family members or business associates. But MPs were cleared to let accommodation out to each other, providing they are not married or related – allegedly allowing them to generate lucrative nest eggs at the public's expense.

But in a letter sent to the Independent Parliamentary Standards Authority (Ipsa) seen by the Daily Telegraph, Mr Bercow said publication of landlords' names "could involve causing unwarranted damage and distress" to MPs.

A spokesman for Ipsa said: "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."

A House of Commons spokesman said: "The Speaker's letter to Sir Ian Kennedy, chair of IPSA, relates solely to the security implications of publishing MP rental details based on professional advice and resolutions of the House.