Over 50 phone-hacking victims have warned the prime minister they will not accept any form of continued self-regulation for the press.
A letter from the victims, organised by the Hacked Off campaign, makes their alarm clear after a series of reports suggesting David Cameron will give newspaper editors another chance to make self-regulation work – even if Lord Justice Leveson's final conclusions recommend otherwise.
The letter's signatories seek reassurances from Cameron that he will consider Leveson's recommendations with an open mind, proceed on a cross-party basis and – critically - ask that he has not already decided in favour of continued self-regulation.
"To remind you once again: you said that the test of the future system of press regulation is not whether it suits the politicians or their friends in the press, but rather the public interest – including the need of members of society to be free from illegal and unethical press practices," the letter states. "Do we have those reassurances?"
A Downing Street spokesperson told the Observer: "We await Lord Leveson's independent report, the content of which is a matter for him."
Actor Hugh Grant, who has been a prominent campaigner involved with the Hacked Off campaign, told BBC1's The Andrew Marr Show that he was deeply concerned by "weird rumblings" emerging from Whitehall.
"All that may come out of Leveson is a suggestion... for there to be an independent regulator, independent of the newspaper but also crucially independent of government," he explained.
"All that is needed is a tiny dab of statute to set this thing up. I do not see the slightest danger to freedom of speech from that."
Cameron refused to give any indication of his personal view before Lord Justice Leveson publishes his recommendations.
But, summing up the debate, he said: "We don't want heavy-handed state intervention - we've got to have a free press... but on the other hand, it's quite clear people have been abused, people's families and lives have been torn up by press intrusion. The status quo is not an option."
Signatories to the letter include singer Charlotte Church, actor Jude Law, comedian Steve Coogan.
Politicians who have signed the letter include Liberal Democrat deputy leader Simon Hughes and Lib Dem former London mayoral candidate Brian Paddick.
They point out that Cameron made clear in his own evidence to the inquiry that the big test for the reforms' success would be if they had the confidence of the victims of phone-hacking.
"The test of a regulatory system is not does that make the politicians happier?" the prime minister said in June.
"The test of the system is: is it going to provide proper protection to ordinary families who, through no fault of their own, get caught up in these media maelstroms and get completely mistreated?"
Cameron may now be minded to support proposals by Lord Hunt and Black for a new contractual self-regulation body to replace the Press Complaints Commission – in spite of victims' backing for court proceedings as a better forum for seeking redress.
"We do not believe these proposals are satisfactory in themselves, that they meet the needs of the victims, or that they will restore public trust," the letter stated.