Ann Clwyd, a Labour frontbencher, wrote to Betty Boothroyd, the Commons Speaker, pressing her to set up a Speaker's Commission to investigate the issue of MPs' ethics.
A separate move came from the Labour MP Bill Michie, a member of both the privileges committee - from which Labour MPs have withdrawn en bloc - and the Select Committee on Members' Interests.
Mr Michie warned that he and the other Labour members of the members' interests committee would boycott any private investigation into the Paris hotel holiday enjoyed by Neil Hamilton, the corporate affairs minister, at the expense of Mohamed al-Fayed, chairman of Harrods.
Alex Carlile, the Liberal Democrat frontbencher, has requested that the committee's Tory chairman, Sir Geoffrey Johnson-Smith, set in train a formal inquiry into Mr Hamilton's failure to register the gift in the Register of Members' Interests. The members' interests committee almost always interviews witnesses behind closed doors.
Mr Michie said yesterday: 'In the circumstances now prevailing it would be totally anomalous if we made a distinction between this committee and the Committee of Privileges, where we are totally opposed to secrecy.'
The idea of a Speaker's Commission, in which figures from beyond Westminster would be involved, originated with Dale Campbell-Savours, Labour MP for Workington and a specialist on constitutional affairs.
Ms Clwyd said: 'It is not just a question of deciding whether there should be a public or private inquiry. The reputation of the entire body of MPs is now under attack.'