Hugh Grant: What I want from the Leveson Inquiry report
28 November 2012 Last updated at 09:30 GMT
More than 80 MPs and peers have written to two national newspapers opposing any new laws to regulate the press.
The warning comes as Prime Minister David Cameron prepares to receive a report by Lord Justice Leveson on media ethics, ahead of Thursday's publication.
The cross-party group says any kind of state regulation would damage press freedom.
But the actor Hugh Grant, who speaks for the campaign group Hacked Off, says he wants an end to newspapers ''marking their own homework''.