The plans come in the wake of the Leveson report into the press
The UK’s political leaders are making a final attempt to build support for their rival plans on press regulation.
David Cameron is facing defeat in the Commons unless he can persuade MPs from other parties to support his proposals.
Lib Dem leader Nick Clegg and Labour’s Ed Miliband back his idea of a watchdog set up by royal charter but want it to be created in law.
In an Observer interview, Mr Miliband has urged MPs to “stand up for the victims” of press abuse when they vote.
The plans follow the phone-hacking scandal and Lord Justice Leveson’s inquiry into press ethics.
Both sides have now adopted the idea of creating a new press self-regulatory body by a royal charter – a formal document used to set up bodies such as universities and the BBC. But the major sticking point remains whether it should be set up by a law.
Mr Cameron believes enshrining the royal charter in law will harm press freedom but Deputy Prime Minister Mr Clegg and Mr Miliband say the rules will lack impact without it.
The other main differences in the rival royal charter, which Mr Clegg launched with Mr Miliband, involve not giving the press a veto over the members of the regulator and preventing it from being watered down or strengthened by future governments.
BBC political correspondent Tim Reid reports that sources close to Mr Cameron are refusing to reveal whether he is optimistic about winning parliamentary backing for his royal charter but say he would continue to make the case for its proposals ahead of Monday’s debate and vote.
The prime minister’s allies have spent the weekend trying to persuade potential Tory rebels they should support his plans, our correspondent added.
Speaking to the Observer, Mr Miliband said: “Monday is the day that politics has got to do the duty by the victims and has got to stand up for the victims.
“I think it is an important moment because we have had decades of failing to ensure that we have a system of press complaints and redress which means that ordinary people aren’t left at the whim of a sometimes abusive press.”
He said when MPs vote they should break with the past when “politicians were fearful of speaking out because they thought; ‘I’m going to get bad publicity; it will turn the press against me’.”
The prime minister pulled the plug on cross-party talks on the issue on Thursday but has indicated he would abide by parliament’s decision.
Mr Cameron insists his proposal is “the fastest possible way to deliver the strong self-regulation body that Leveson proposed that can put in place million-pound fines, prominent apologises and get justice for victims in this country”.
But he said on Saturday he was “delighted” with the “real progress” that had been made and that Mr Clegg and Mr Miliband had now “dropped many of their previous unworkable demands”.
“They don’t want to have some all-singing Leveson law, which I think would have been bad for our country,” he said.
Lord Justice Leveson’s 2,000-page report, published in November, found press behaviour was “outrageous” and “wreaked havoc with the lives of innocent people”.
It recommended that the press should set up a tough new independent regulator, and that the system should be underpinned by legislation to ensure it was effective.
The parents of murdered schoolgirl Milly Dowler have said they were “disappointed” that the report’s recommendations may not be taken forward.
The News of the World was closed shortly after it was found Milly’s phone had been hacked and Bob and Sally Dowler said the proposals aimed to prevent “the sort of abuses that we and so many others suffered”.
Hacked Off, the campaign group representing some press abuse victims, has been leading calls for full implementation of the Leveson report.
But one of its key figures, the actor Hugh Grant writing in the Observer, said the campaign has “reluctantly accepted that a royal charter could be the way to give backing to the new system”.
He added that Mr Cameron faced “possible defeat” because he was “so clearly on the wrong side in this”.