LONDON -- Prime Minister David Cameron announced on Thursday that cross-party talks with other political leaders on regulating Britain's rambunctious press had broken down and that he would pursue his own proposal for a system of self-regulation after months of inquiries into the phone hacking scandal, mainly at Rupert Murdoch's tabloid newspapers here.
Mr. Cameron's abrupt move placed new strains on his relationship with the Liberal Democrats, the junior coalition partner with his Conservative Party, and raised the possibility that Liberal Democrats may end up voting with the Labour opposition against Mr. Cameron's proposal for a royal charter to underpin a new self-regulatory body.
The prime minister's action also underscored the divisiveness of the debate about press regulation, at present supervised by a self-regulatory body generally seen as a feeble restraint on newspapers with a reputation for a headlong pursuit of scoops and a frequent disregard for the privacy of politicians, celebrities and others.
In November, after months of hearings, a long-awaited report on the behavior of British newspapers embroiled in the phone hacking scandal, written by Lord Justice Sir Brian Leveson, recommended that press regulation be backed by parliamentary statute, curbing Britain's 300-year-old tradition of broad press freedom.
The Leveson inquiry was established after the hacking scandal came to a head in July 2011. At that time, Mr. Murdoch ordered the closing of The News of the World, a flagship Sunday tabloid, after disclosures of widespread hacking, including the cellphone of Milly Dowler, a kidnapped schoolgirl who was later found murdered.
The crisis led to civil suits, criminal investigations, a parliamentary inquiry and the Leveson hearings -- scrutiny that coursed through British public life, exposing previously hidden relationships between the press, the police and politicians.
The affair has cost Mr. Murdoch's newspapers hundreds of millions of dollars.
Six more journalists who previously worked for The News of the World were arrested in February on suspicion of hacking into cellphone messages, adding to a tally of more than 100 reporters, editors, investigators, executives and public officials implicated in wrongdoing by police units investigating accusations of criminal activity.
The scandal spread on Thursday to the rival Mirror Group, when the police said that four of the group's journalists had been arrested in south London on suspicion of "conspiracy to intercept telephone communications." The journalists were not identified by name. Scotland Yard said they were three men ages 40, 46 and 49, and a 47-year-old woman.
British news reports said all four were all senior serving or former editors, including the editor and deputy editor of the tabloid Sunday People and the former editor and former deputy editor of the tabloid Sunday Mirror.
When the Leveson inquiry published its report calling for statutory underpinning to a new press watchdog, Mr. Cameron opposed the idea while Labour supported it.
Instead, Mr. Cameron proposed that a new self-regulatory agency with the power to fine newspapers and take other measures to support victims of press intrusion into their privacy should be supported by a royal charter, a device used to give authority to and define the rights of major institutions like the British Broadcasting Corporation and the Bank of England.
Mr. Cameron plans to call a vote on his proposal in Parliament on Monday, but Liberal Democrat officials said it was unclear how the junior coalition partner would vote. The Press Association news agency quoted Liberal Democrat officials as saying Mr. Cameron called off the talks with their leader, Nick Clegg, and the Labour opposition leader, Ed Miliband, "unilaterally."
"We were very surprised and disappointed," an unidentified Liberal Democrat official was quoted as saying. "We thought we were making real progress and inching toward a deal, but the Prime Minister has unilaterally decided to pull the plug on cross-party talks."
Mr. Clegg did not say which way his followers would vote on Monday. "Clearly, there are several days to go before votes are held," he was quoted as saying, "and in those days I will be working flat-out speaking to other politicians from other parties to make sure that, whatever David Cameron has decided, that we nonetheless work together to get a proper solution to this difficult problem."
"Clearly I don't agree with David Cameron's approach, because I don't think it goes far enough to make sure that we deliver on the central recommendations of the Leveson report."
At a news conference on Thursday, Mr. Cameron said his proposal would create "the toughest regulation of the press that this country has ever seen."
Newspapers, he said, would refuse to accept regulation by parliamentary statute -- an idea supported by Labour, the Liberal Democrats and privacy campaigners.
"There's no point in producing a system that the press won't take part in," Mr. Cameron said. "As prime minister, I wouldn't be fulfilling my duty if I came up with something knowing that it wouldn't work."
This article originally appeared in The New York Times.