MPs' expenses: Sir Thomas Legg explains his rule change

Sir Thomas, a former senior civil servant, is writing to every MP about their second home expenses claims between 2004 and 2008.

Some are being told that their claims were excessive and they should pay back money. Some are being asked for more information and some are being told they are in the clear. Most controversially, Sir Thomas has imposed limits on the amounts MPs should have been allowed to claim for categories including cleaning and gardening.

The caps – of £2,000 a year for cleaning and £1,000 for gardening – were the cause of more than £10,000 of the total £12,500 paid back on Monday by Gordon Brown.

Sir Thomas's letters have been accompanied by a note in which he explained his decision.

He told MPs that there had effectively already been a limit on the amount that could be claimed for mortgage interest, because the total additional cost allowance budget prevented an annual claim of more than about £24,000 last year.

Household goods, he said, were also subject to limits. The so-called "John Lewis list", which was kept secret from MPs, told Commons officials that they could allow, for example, up to £750 for a television and £10,000 for a new kitchen.

However, Sir Thomas said that he could find nothing in the existing rules setting out the maximum allowable for other large expenses, including cleaning and gardening. Therefore, he believed that limits must be imposed retrospectively.

"Some limits must be regarded as having been in place to prevent disproportionate and unnecessary expenditure from the public purse," he said.