The revelations come on top of the plans that emerged on Tuesday that MPs whose local railway station is within 60 minutes of Westminster would not be entitled to second-home payments, that the allowances would cover only rent, not mortgage interest, and that relatives would be banned from working in Parliament.

Downing Street made clear pearl jewelry yesterday that MPs who objected would not be given a chance to overturn the report in the Commons. It issued a statement saying that a minister, likely to be Harriet Harman, the Leader of the House, would make a statement after the report is released on Wednesday. MPs will be given a chance to debate it. It will be for the Independent Parliamentary Standards Authority (IPSA), however, to devise and administer the new scheme, which will come in after the general election.

“The Parliamentary Standards Act provides that the IPSA must consult MPs when drawing up the expenses regime, but not seek their final approval,” a Downing Street spokesman said.

“They will not need to seek Parliament’s consent for the expenses regime. MPs have agreed the Parliamentary Standards Act that takes the pearl jewelry wholesale setting of their expenses out of their hands.” This appeared to be an attempt by some senior MPs to find a way of voting down the proposals.

MPs tried to argue yesterday that their right to claim mortgage interest on their second homes was enshrined in legislation passed by John Biffen, the former Tory leader of the House, in 1985. They said that fresh legislation was needed to overturn the rules, which would have to be debated in the Commons and then voted on — presenting an opportunity to throw out Sir Christopher’s proposals.

Downing Street said that it had checked with its lawyers, and MPs would not be able to force a vote wholesale pearl jewelry this way. However, its argument was undermined when it emerged that Jack Straw had promised the Commons on June 29 that it would get the right to “approve” the Kelly proposals.