Sir Patrick Cormack, shadow deputy leader of the House, demanded that privilege - and its protection from libel actions - should be used only when an MP can prove that allegations have "real substance".
The 1689 Bill of Rights states that "freedom of speech and debates or proceedings in Parliament ought not to be impeached or questioned in any place or court outside Parliament", effectively allowing MPs to level whatever accusations they like against outsiders.
Tory MPs were furious that Peter Bradley, the Labour MP for The Wrekin, gave details of drugs and money-laundering investigations in which Michael Ashcroft's name had featured, before admitting he had no idea whether the Tory treasurer had done anything wrong.
The latest exchanges may reignite proposals that were being considered last year to give a right of reply to anyone named by an MP under Parliamentary privilege. It is a privilege, however, that few MPs would like to see diluted because of its effectiveness of airing matters that would otherwise remain secret.
Civil rights lawyers yesterday advised against changing the rules. "Parliamentary privilege is a fundamental safeguard for free speech in a democratic society," said Mark Stephens of Stephens Innocent, libel lawyers who represent the New York Times, The Wall Street Journal and Washington Post in the United Kingdom.