The prime minister made clear he expected such transparency in a meeting yesterday with Labour chief whip Geoff Hoon.

The move, in the wake of the Derek Conway controversy, was announced after Cameron today appeared to lead efforts for greater transparency by conducting a survey that reveals more than 70 Tory MPs employ members of their family.

The shadow cabinet has now been asked by Cameron to declare in the register of members' interests any relatives they employ from the beginning of the new financial year on April 1.

Cameron said: "We have carried out a ring-round among almost all the Conservative members of parliament and there are just over 70 who employ husbands or wives or family members.

"There is a need for greater transparency and greater openness when it comes to MPs' pay and MPs' staff and the use of the expenses and allowances.

"As the first step, I will be asking my frontbench colleagues from April 1 to register... if they do employ a member of their family."

The move is designed to draw a line under the Conway debacle and restore credibility to the party. The disgraced Tory MP was suspended from parliament for ten days yesterday over excessive payments to his son at taxpayers' expense.

"I believe the public are right to demand more transparency and openness when it comes to MPs' staff, pay, allowances and expenses", said Cameron.

"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.

"This is 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."

The prime minister yesterday backed calls for more transparency in the spending of MPs' taxpayer-funded allowances.

Brown's official spokesman said today: "The prime minister has already made clear in his discussions with the chief whip that all Labour MPs, not just the frontbenchers, should be open and transparent about the staff who are working for them and, in light of the scandal involving Mr Conway, that includes identifying any family members.

"But the important thing is not just that the staff are registered and identified appropriately but that they are doing the job for which they are funded by the taxpayer.

"That's what Mr Cameron and his party have previously failed to recognise."

Brown is expected to meet Labour's parliamentary committee on Wednesday to discuss the ways in which MPs' spending could be made more transparent. MPs are responsible for recruiting staff to help them in their parliamentary work, and many employ spouses or other relatives to work on their team.

But the practice came under the spotlight this week after it emerged that Conway paid his son Freddie £45,000 over two-and-a-half years while he was studying full- time at Newcastle University.

MPs endorsed the recommendation of the Commons Standards and Privileges Committee to suspend Conway and order him to repay £13,161. The standards commissioner, John Lyon, is considering a new complaint against Conway concerning his elder son Henry, who is said to have received £32,000 for research work.

Police are meanwhile considering a complaint that Conway committed offences under the Fraud Act.

Conway said on Wednesday he would stand down from the Old Bexley and Sidcup constituency at the next election.