British Members of Parliament (MPs) who claimed for "phantom" mortgages on their expenses should be investigated and prosecuted, Tory leader David Cameron said on Saturday.

The MPs who had committed a crime with their expenses claims should "face the full force of the law," Cameron said in an interview with the Daily Telegraph, the first paper to reveal the expenses scandal.

"I've said it's not for me to call in the police, but the police know what the law is. And if they feel it's been broken they should be able to look at that without fear or favor," Cameron said.

Scotland Yard is currently considering whether to launch criminal inquiries into any potential fraudulent claims.

Cameron's call came as former environment minister, the Labour Party's Elliot Morley became the latest MP to announce he will not contest the next general election.

Morley had claimed 16,000 pounds (about 25,000 U.S. dollars) in mortgage interest payments, 18 months after the mortgage was paid off.

He has apologized and repaid the money, but blamed his expenses claims on "sloppy accounting," as opponents urged him to quit immediately rather than to wait until the next general election.

Morley made his announcement of stepping down on Friday night, following a meeting with local Labour Party officials at his Scunthorpe constituency.

He said the pressure had been affecting his family and his health, and insisted the decision was his own.

Thirteen MPs have announced their intention to step down since details of the expenses scandal were first published.

Two other MPs of the Labour Party -- David Chaytor and Ben Chapman -- have also admitted "errors" in claiming for mortgages that had already been paid off.

Meanwhile, Tory MP Bill Wiggin blamed the Commons Fees Office for not correcting his repeated "mistake" when he claimed for a mortgage on his constituency home rather than his second home in London.

Tory MP Humfrey Malins told the Telegraph that he spent two nights a week in his taxpayer-funded second home in London, in which his children have stayed rent-free.

Meanwhile, a Populus poll in Saturday's Times newspaper provided gloomy reading for Prime Minister Gordon Brown, with the Labour Party at its lowest-ever national rating following the exposure of the scandal.

According to the poll conducted on May 26-27 on a sample of 1,001 adults, the Labour Party trailed in third place after the UK Independence Party, with just 16 percent of respondents prepared to vote for Labour in next week's European elections.