More than 70 Conservative MPs employ relatives as members of their personal staff, the party's leader David Cameron said today.
The disclosure comes after Conservative MP Derek Conway was suspended from the Commons for 10 days for paying his son almost £50,000 of taxpayers' money for work he apparently never did.
Mr Conway, who says he will quit politics at the next election, has been expelled from the parliamentary Conservative party and could face a police inquiry.
MPs are allowed to employ relatives out of public funds and some pay their wives or husbands to work as secretaries, saying it can help marriages to survive long hours or living apart.
But the scandal surrounding Mr Conway, who had also employed his other son as a researcher and his wife as his secretary, has prompted calls for greater disclosure over the practice.
"I believe the public are right to demand more transparency and openness when it comes to MPs' staff, pay, allowances and expenses," said Mr Cameron.
"As a first step I will ensure that from the start of the new financial year (April 1st 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."
Cameron said he had asked earlier this week how many of his party's MPs employed family members had been told there were over 70.