MPs were embroiled in a new expenses row today after it emerged that 27 are letting out London homes at the same time as claiming public money to rent in the city.

Shadow ministers Jim Murphy, MP for East Renfrewshire, Andy Burnham, and Chris Bryant; Communities Minister Don Foster; and former defence secretary Liam Fox are among those listed as raking in income from properties while receiving up to £20,000 a year in expenses.

Although the practice does not break any rules, it will fuel concerns that politicians are still able to profit from Commons allowances.

The Independent Parliamentary Standards Authority's (Ipsa) blanket ban on MPs claiming mortgage interest came into effect this summer. They are now only permitted to receive expenses for renting.

The move was intended to head off criticism after the scandal three years ago showed politicians had been using public money to build up property portfolios.

However, it also appears to have created an incentive for many to vacate homes they own.

Research by the Daily Telegraph identified Tory MPs David Amess and Peter Luff, and Liberal Democrat ex-defence minister Nick Harvey among those letting out properties in the capital while also claiming expenses for renting.

The names could only be deduced because Ipsa last night released partial postcodes of taxpayer-funded second homes - which could then be cross-referenced with the parliamentary register of interests.

The disclosure followed linked concerns that MPs are able to exploit a "loophole" in the rules to rent properties to colleagues, who then claim the costs on expenses.

It is understood that four MPs are currently renting from four other MPs - although there are no cases of home "swaps".

Linda Riordan, the Labour MP for Halifax, lets her London flat to fellow Labour MP Iain McKenzie for £18,720 a year.

Mr McKenzie said: "If I had known beforehand that the flat was owned by an MP then I probably wouldn't have taken it. You've got to apply the test of how it looks to the man in the street, regardless of whether it's above board or not."

Yesterday, Commons Speaker John Bercow was accused of trying to suppress details of the matter after warning Ipsa that revealing the identities of politicians' landlords would be a "security risk".

The watchdog had been due to disclose the material in response to another Freedom of Information (FOI) request.

However, the process has now been put on hold in the wake of Mr Bercow's intervention.

In a letter to Ipsa, Mr Bercow insisted there was a "very real danger" that MPs' residential addresses could be discovered as a result of the planned publication.

Responding to the Speaker's letter last night, Sir Ian Kennedy, chairman of Ipsa, insisted the authority "would not, under any circumstances, release the full address" of an MP.

But he added: "The policy also makes clear that we would release, on request, the names of landlords and other suppliers of goods and services where this was in support of a claim made under the scheme for business costs and expenses."

Sir Ian said all affected MPs had been contacted, asking if they had concerns about the release of their landlord's details.

However, only a third - 110 - replied. Some 60 have indicated they have no problems with the disclosure, and 50 expressed reservations.

"We are therefore delaying our response to the FOI request and will be writing to those MPs concerned to give them a further two weeks to respond," he said.

Tory Sarah Wollaston said she had grave concerns about revealing MPs' addresses, having had her London flat and constituency home broken into.

The Totnes MP said she agreed with the need for transparency, but was worried about a tiny minority of people, including activists, using the information maliciously.

Dr Wollaston said: "I am very happy for everyone to know that I have no connection with my landlord in my London address - I have never met them and I don't think they even live in this country.

"But if they (Ipsa) publish politicians' home addresses then you are exposing them (MPs) to very difficult situations."

Matthew Sinclair, chief executive of the TaxPayers' Alliance, said: "If MPs are again found to have exploited the expenses system, it will be another stain on the reputation of Parliament.

"It was the cry that 'it's all within the rules' combined with attempts to suppress the publication of claims that made the MPs' expenses crisis three years ago so toxic. Whilst the rules may not technically prevent MPs from renting properties to one another, it is certainly against the spirit of those rules.

"The public's faith was left in tatters in 2009 and the latest allegations could endanger much of the work that has been done since then to restore public confidence in our politicians.

"It is vital that there is total transparency in all matters relating to MPs' taxpayer-funded expenses and allowances."