David Cameron promised last night to repay £22,000 of expenses if he is found by the Tory scutiny panel to have behaved unreasonably over his mortgage arrangements.

The Conservative leader is to be examined by the panel over a £350,000 interest-only mortgage that he took out to buy a house in Oxfordshire when he became an MP in 2001.

The panel will have to decide whether it was reasonable for Mr Cameron to have paid off separately £75,000 from his London home mortgage four months after buying the Oxford property, rather than using the sum to reduce his taxpayer-funded loan. Had Mr Cameron done so, it is estimated that he could have saved the taxpayer about £22,000 in mortgage payments.

In an interview with Channel 4, he said:“What I did was, as I became an MP, I bought a house in my constituency, and took out — yes — quite a large mortgage, three hundred and fifty thousand. And I claimed the mortgage interest on that. But I was actually paying out more in mortgage interest than I was claiming from the taxpayer . . . I don’t believe that had the mortgage been somewhat smaller, it would have made any difference. One, because I was paying more out in mortgage interest. And secondly, because when I did manage to pay down some of the mortgage, which I did in 2007, I then claimed for some very basic bills — things like electricity and gas and water.”

Mr Cameron was forced to defend his mortgage arrangements amid another slew of damaging MP expense abuses from all three main political parties. It emerged at the weekend that Frank Cook, a Labour backbencher, asked the taxpayer to reimburse a £5 donation that he made at a Battle of Britain memorial service. The claim was rejected by the Parliamentary fees office. Mr Cook apologised yesterday and explained that the claim had been submitted in error.

It also emerged that Charles Kennedy, the former leader of the Liberal Democrats, charged the taxpayer for three boxes of mints and two House of Commons teddy bears at a total cost of £35.75. Mr Kennedy said that he had made the claim in error and had repaid the money. It was also revealed that he had asked the taxpayer to reimburse him for Remembrance Day poppy wreaths. While one claim, for £18, was signed off by the fees office in November 2006, one for £49 the following year was rejected. Mr Kennedy said that the initial claim was made by mistake and that he had paid the money back.

Roger Godsiff, the Labour MP for Birmingham Sparkbrook, was reported to have made expense claims for two bath mats for £13.98 and for £69.98 to reimburse him for a lawnmower. He also claimed for a hedge trimmer. Tim Yeo, the Tory MP for South Suffolk, charged the taxpayer for a £900 pink laptop.

Mr Cameron said yesterday that Eleanor Laing, his Shadow Justice Minister, would have to return money to the taxpayer after avoiding capital gains tax on a second-home sale.

He also sought to support Michael Gove, the Shadow Secretary of State for Children, Schools and Families, who claimed £7,000 to furnish a property. The Tory leader said: “He did make a big claim for furniture. That was completely within the rules. I don’t like that expression ‘within the rules’. I know it drives people mad. But I think paying the money back, which he has done, is the appropriate thing to do.”

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