Labour and the Liberal Democrats joined forces to publish a “strengthened version” of Prime Minister David Cameron’s proposed royal charter to establish a new watchdog.
They signalled they still believed legislation was required to underpin an independent self-regulatory body, as recommended by the Leveson Inquiry into phone hacking.
That leaves them firmly at odds with Mr Cameron, who believes that would threaten press freedom and make the system unworkable as newspapers would refuse to sign up.
Yesterday’s publication of the rival draft royal charters exposed the main remaining areas of difference between the two sides of the argument.
Labour leader Ed Miliband said the Lib-Lab version differed from the Tory plan as it was underpinned by statute, while the proposed regulator would be independent of the press, with the industry’s power of veto over appointments removed. The regulator would also able to investigate and ensure a proper and prominent apology was made.
Mr Clegg said it was “a strengthened version of the royal charter that can deliver what Leveson wanted”.
MPs will vote on Monday on an amendment to the Crime and Courts Bill that would enable the courts to impose “exemplary damages” in libel cases and other civil actions on newspapers that had not signed up to the regulator.
Mr Cameron regards the measure as essential to his scheme by acting as a spur to newspapers to sign up to a regulator system he says would be the toughest ever in Britain.
Allies acknowledged there was a “strong chance” it would be defeated, however, as the Tories have no overall majority in parliament and are opposed by their coalition partners.
The Prime Minister said: “It seems to me that the other parties are moving away from a sort of full-on legislation on Leveson and accepting that a royal charter is the right way forward.”