In another dramatic day in the saga that has killed off the News of the World tabloid and wrecked Murdoch's takeover bid for pay-TV giant BSkyB, the Murdochs reversed their earlier refusal to give evidence to MPs on Tuesday.
Police also arrested Neil Wallis, a former News of the World executive, but were later forced to admit that Scotland Yard itself had previously employed him as an advisor, raising fresh concerns about police corruption in the case.
The Murdochs' climbdown came only five hours after parliament's media select committee formally summoned them to attend, having received letters from the pair saying they were "unable" to attend but giving no reasons.
That left Rebekah Brooks, the chief executive of Murdoch's British newspaper arm and a former editor of the News of the World from 2000 to 2003, to appear by herself before the committee.
But a spokesperson for Murdoch's News Corp. later said: "News Corp can confirm that we are in the process of writing to the select committee with the intention that James Murdoch and Rupert Murdoch will both attend on Tuesday."
Committee chairperson John Whittingdale had said that if the Murdochs did not answer the summons then the matter would be dealt with by the House of Commons, which can then order the person to attend.
"If that is not obeyed then it becomes a matter of contempt of parliament and there are penalties," he said, adding: "I understand that it can include imprisonment."
For the tabloid's ex-editor Brooks, it promises to be a tough session.
At her last committee appearance in 2003 she admitted: "We have paid the police for information in the past", though she later said she was referring to the industry in general.
The extent of those payments is part of a Scotland Yard investigation which is also dealing with the voicemail hacking, and of a full public inquiry announced by Prime Minister David Cameron.
Australian-born Murdoch has been in London in crisis mode since Sunday, the day the 168-year-old News of the World published its last ever edition.
The row had rumbled on for months but exploded last week after it emerged that the paper had targeted the messages of Milly Dowler, a murdered 13-year-old girl, and of the families of the veterans of the wars in Afghanistan and Iraq.
On Wednesday, Murdoch's News Corp announced it was dropping its bid for full control of BSkyB, whose portfolio includes live English Premier League football and blockbuster films and has 10 million household subscribers.
In London, police arrested Wallis, 60, the former executive editor and deputy editor of the News of the World, who left the paper in 2009. Wallis is the ninth person to be arrested since the inquiry was reopened in January.
Wallis was deputy editor from 2003 to 2007 under editor Andy Coulson. Coulson quit the paper in 2007 after its royal reporter and a private investigator were jailed for hacking mobile phone voicemails.
Coulson, who went on to become Prime Minister David Cameron's media chief before quitting that job in January, was arrested on Friday in connection with the scandal and later bailed.
But Scotland Yard later confirmed that a media company owned by Wallis "was appointed to provide strategic communication advice and support to the MPS (Metropolitan Police Service)".
It said the contract, which ran from October 2009 to September 2010, included advice on speech writing and public relations, while the police force's deputy director of public affairs was on sick leave.
Wallis was previously a member of the Press Complaints Commission, the British newspaper industry's self-regulating body which now faces reform.
Separately British detectives have told the cousin of Jean Charles de Menezes, a Brazilian man shot dead by police in London in 2005 after being mistaken for a suicide bomber, he may been targeted by the News of the World, campaigners said.
In Australia, the birthplace of Murdoch's global empire, Prime Minister Julia Gillard said on Thursday she would be open to an inquiry into media regulation and ownership after the "disgusting" scandal engulfing News Corp.
In Washington, Democratic senators Jay Rockefeller and Barbara Boxer urged US Attorney General Eric Holder and the Wall Street watchdog Securities and Exchange Commission to launch investigations into the scandal.