MPs will have to list family members who work for them in the parliamentary register of interests, under plans to be voted on in the Commons within weeks, The Times has learnt.

A new 11th column in the register is to be introduced, obliging MPs to disclose family connections fully by April 1. MPs who breach the rule will be investigated by the Parliamentary Commissioner for Standards, brought in front of the Commons Standards and Privileges Committee and could be forced to apologise or face suspension from the House.

In a challenge to the authority of the Speaker, Michael Martin, the move is taking place without him being consulted, and will come months before his own “root and branch” review of the system is done.

The new rules are to be proposed formally by the Standards and Privileges Committee, which is producing a report to be voted on by the floor of the House. It is highly likely to pass, since none of the main parties and few backbenchers will want to be seen opposing the move in the light of the Derek Conway scandal.

It is also likely to put Sir George Young, the committee chairman, on a collision course with Mr Martin. Sir George has made little secret of his desire to sit in the Speaker’s chair, and stood for the post in 2000.

A source close to the committee said that there had been no need to consult the Speaker. “The registrar of members’ interests reports to us, and we have a locus as far as the register is concerned. We have a member of the committee also on the Speaker’s committee.”

Last week, Mr Martin had a confrontation with David Cameron over the Tory leader’s plans for his MPs to publish full details of their expense claims from April. Mr Cameron is said to have refused the Speaker’s demands to call off a press conference announcing the move and was accused of undermining the Speaker’s inquiry.

Two senior Labour figures, Alan Milburn, the former Health Secretary, and Lord Soley, who was the head of backbench Labour MPs, challenged the Speaker’s handling of the expenses debate publicly at the weekend.

Mr Milburn said that Mr Martin had not acted quickly enough over the widespread “fiddling” of expenses.

Some MPs have suggested that the inquiry into expenses should not be conducted by MPs but should be handed over to the independent Committee on Standards in Public Life.

Mark Field, the Conservative MP representing the City of London, has become one of the first members to call publicly for the scrapping of the additional costs allowance, the £23,000-a-year fund for MPs’ second homes. In a letter to the Speaker, Mr Field, who, like other inner London MPs, cannot claim the allowance, said the situation was “tarnishing the reputation of all members and bringing the House of Commons into disrepute”. He added: “For many years becoming a Member of the European Parliament was perceived by the public as joining the ‘gravy train’. We now have the similar epithet being used for the British Parliament.”

A number of loopholes have come to light in recent days, including the disclosure that 44 MPs are renting out one property while the taxpayer pays the mortgage costs or rent on a second.

One MP, who would not be named, said colleagues use the additional costs allowance to buy a place in London. After a few years, the allowance goes up and they can get a bigger mortgage. Instead of selling the first place, they keep it and buy a second. They pay the mortgage on the first by renting it out and pay the new mortgage from the allowance. When they cease to be an MP, they can sell and make a profit. “It’s like buy-to-let financed by the taxpayer,” the MP said.

Michael Ancram, the multi-millionaire Tory MP, was under pressure to explain what he had spent £89,927 of the additional costs allowance since 2001, when he owns his three properties, worth an estimated £8 million, outright.

He said he spent the money running his constituency mansion in Wiltshire, including repainting walls and removing moss from the garden, but he insisted he was entitled to the money under the rules.

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