Over 70 Tory MPs employ relatives

Mr Cameron said he has asked all his frontbench team to declare any such arrangements publicly from April 1 as a "good first step".

He 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."

Mr Cameron continued: "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."

Mr Conway was suspended from the Commons for 10 days on Thursday and ordered to repay up to £13,161 he had improperly awarded to his son Freddie.

The Old Bexley and Sidcup MP, who had already been stripped of the Tory whip by Mr Cameron, has announced he will not seek re-election. He could also face a police investigation and a fresh sleaze investigation into complaints made about payments to his other son, Henry.

The case has focused attention on the employment by MPs of family members - Mr Conway's wife worked for him as well.

One standards watchdog has suggested a ban could be required if tighter scrutiny cannot be enforced, with spot checks of MPs' spending also suggested.

Mr Cameron rejected calls for a ban, insisting many family members worked very hard for the money but said he would welcome the idea of spot checks. "Many MPs you will find who have had a long-standing arrangement with a wife who is a secretary working very hard, sometimes in the constituency, sometimes in London. What matters is, is the work being done?" he said.

Meanwhile, Gordon Brown is to tell Labour MPs to declare publicly any family members they employ amid fresh efforts by politicians to limit the damage of the Derek Conway controversy. The Prime Minister made clear he expected such transparency in a meeting with Chief Whip Geoff Hoon, his political spokesman said.