Tom Gordon, Michael Settle, and Paul Hutcheon Tavish Scott, the Scottish Liberal Democrat leader, and four of his MSPs are under pressure not to keep any profits they may make on the future sale of their second homes in Edinburgh.

Nick Clegg, the LibDem UK party leader, yesterday said MPs of all parties should get "out of the property game altogether".

and said his benches were committed "to handing back to the taxpayer every pound of any gain made when second homes are sold which were funded by the taxpayer."

However, the Holyrood Lib- Dems, who are currently billing taxpayers for mortgage interest on their second homes, are not planning to follow suit.

The party last night insisted the expenses systems were different at the two parliaments, and pointed out an independent review of allowances last year in Holyrood had rejected "clawing back" the profit on second homes.

Last night more startling new revelations about MPs expenses emerged which could lead to a possible criminal investigation.

Elliot Morley, the former agriculture minister in the Labour government, claimed parliamentary expenses of more than £16,000 for a mortgage that had been paid off 18 months earlier.

The MP for Scunthorpe claimed £800 a month from the public purse on mortgage interest payments on his constituency home after they stopped in March 2006.

Legal experts suggested Mr Morley may be open to prosecution for fraud or theft, despite his apology last night. Mr Morely said he had informed the chief whip and the parliamentary fees office.

He added that he has already repaid some of the money.

Fabian Hamilton, another Labour backbencher, declared his mother's London house as his main residence while over-charging the taxpayer by thousands of pounds for a mortgage on his home in his Yorkshire constituency.

The Leeds North East MP defended his arrangement by saying he spent most of his time in the house owned by his mother, a retired judge, until her death in 2005. The designation of the London house as his main residence enabled him to claim thousands of pounds for his family home in Leeds.

Embarrassingly for Tory leader David Cameron, John Maples, the party's deputy chairman, declared a room in a private members' club in London's Pall Mall as his main home, which meant he could spend money on his family's Oxfordshire home. Last night he denied any wrongdoing.

Stephen Crabb, a Conservative MP, said his main home was a room in a flat rented by another MP after he bought a new family home in Wales. Meanwhile, in Scotland, Tavish Scott and four of his MSPs were criticised by a spokesperson for the Taxpayers Alliance over their stance.

He said: "Liberal Democrats should stand behind Nick Clegg on this proposal, as it is a sensible idea."

Mr Clegg told BBC Radio 4: "I have said I will voluntarily make sure that any money that is gained from the sale of my house goes back to the taxpayer. I also now say that the Liberal Democrat shadow cabinet will do the same until new rules are in place."

A Scottish LibDem spokeswoman said: "All of the (Lib- Dem) MSPs in Edinburgh are not planning to sell them. Our next election is not until 2011 and it's an entirely hypothetical question."

Three of the LibDems' properties are understood to have risen substantially since they were bought as second homes.

Mr Scott, Scottish leader since August, has already made a £36,000 profit on a publicly-supported flat in 2005. He is now sitting on a potential profit of £120,000 at a second property bought the same year.

Despite the fall in property prices in the capital, Mr Scott's family home in Morningside, bought for £380,000, is estimated to be worth around £500,000.

Mr Scott is claiming £11,900 a year for mortgage interest payments for the property.

Since 2002, he has claimed more than £61,000.

Nicol Stephen, Mr Scott's predecessor as LibDem leader, stands to make a £200,0000 profit on his Morningside home. Bought for £193,333 in 2002, it is currently estimated at £400,000. The taxpayer has so far paid £51,495 for Stephen's mortgage interest.

Former agriculture minister Ross Finnie's modest flat off Leith Walk is estimated to be worth £60,000 more than he paid in 2001. His mortgage interest claims to date are around £17,000.

"I don't think we are comparing apples with apples here," he said when asked if he would be willing to repay the profit to parliament.

Backbencher Jamie Stone, who bought a flat just before parliament stopped MSPs starting new claims for mortgage interest, is breaking even after claiming £8492 mortgage interest.