David Cameron has acted in an attempt to pre-empt any further unwelcome Sunday newspaper coverage about Tory MPs using public money to employ family members. He announced today that more than 70 of his 198 MPs do so.

Among that number is Mr Cameron himself. Party officials confirmed that Alice Sheffield, his wife's half-sister, works in the Conservative leader's correspondence unit.

Mr Cameron said that he had asked all members of his front-bench to declare whether they employ family members in the Register of Members’ Interests from the start of the next financial year on April 1.

He voiced the hope that other Tory MPs would follow suit, although he has no power to force them and some may not like the idea.

It did not take long for Gordon Brown to try to outdo Mr Cameron in the anti-sleaze 'arms-race'. His political spokesman announced this morning that he expected all Labour MPs to declare publicly any family members. The Prime Minister made clear he expected such transparency in a meeting with the Chief Whip, Geoff Hoon.

The Liberal Democrats have already called for immediate disclosure.

Earlier this week Mr Cameron - in the wake of the revelations about Derek Conway paying two of his sons - asked his staff to explore the extent to which other Tory MPs do it. Conservative high command is well aware that reporters have been working all week to discover whether there are other Conways out there.

The practice happens in all parties and the view from the top appears to be that if it is all declared and above board it is perfectly legitimate for a wife or husband, for example, to do secretarial work for the MP. MPs are responsible for employing their own staff and as things stand there is no established system for declaring their names.

Mr Cameron has moved because the last thing he wants is the memories of sleaze, that so damaged his party in the 1990s, to come floooding back. He delayed 24 hours before removing the whip from Mr Conway but has still been praised for being tough. Now he has acted to stop this issue becoming a running sore.

He said: “As you know, Members of Parliament are responsible for employing their own staff. Earlier this week I asked to be told how many members of my parliamentary party employ family members and there are over 70.

“I believe the public are right to demand more transparency and openness when it comes to MPs staff, pay, allowances and expenses. As a first step I will ensure that from the start of the new financial year (1st April 2008) all Conservative front bench MPs must declare if they employ family members in the Register of Members' Interests. I hope all other Conservative MPs will follow suit.”

He added that this was “the first in a number of steps we need to take to reassure people that Members of Parliament work hard for their constituents and are honest and open in their spending of public money”.

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