The News International chairman has until today to reply to questions asked by the Commons culture, media and sport select committee, following allegations from two former executives at the defunct Sunday tabloid that he was "mistaken" in one of his statements.
Former News of the World editor Colin Myler and ex-legal affairs executive Tom Crone claimed that Murdoch had misled the committee about a key email suggesting that knowledge of phone hacking was more widespread at News International. Myler and Crone also have until today to send letters to the committee clarifying their statements.
The letters, along with another from former News International head of legal affairs Jon Chapman, are expected to reignite the phone hacking scandal.
Committee chairman John Whittingdale previously said that it was "very possible" Murdoch would be asked to reappear after the submissions. Speaking to The Guardian, a source with knowledge of proceedings said: "These letters are going to be dynamite."
The committee considers the matter so pressing that the MPs are returning from their holidays to hold a private meeting next Tuesday to discuss the new evidence.
Murdoch had said that when he signed off a payment of almost £700,000 to phone hacking victim Gordon Taylor, he did so without knowing all the facts. But Myler and Crone have placed question marks over this claim, saying that they did show him an email, known as the 'for Neville' email, which is said to have implied the News of the World's chief reporter Neville Thurlbeck was also implicated in malpractices.
Alongside his knowledge of the key email, it is understood that Murdoch has been quizzed by MPs about payments made to Glenn Mulcaire, the private investigator formerly employed by the News of the World who was jailed for hacking voicemail messages.
In a statement, Murdoch said that he "stands by his testimony to the select committee" but today's letter is expected to provide evidence to back up this claim.
Speaking last month, Whittingdale said that the committee regards the 'for Neville' email "as one of the most critical pieces of evidence in the whole inquiry".
He added: "The areas where I'm particularly keen to get additional information is from Crone, Colin Myler and Jon Chapman, where they say the evidence we were given by James Murdoch was wrong.
"So what we've agreed to do is to ask them to give us those extra details. When we have received that response we may well wish to call them in and take oral evidence. On the basis of that I think it's very possible we will want to put those points to James Murdoch."
Yesterday, a 61-year-old man was arrested on suspicion of phone hacking by the Metropolitan Police, with reports indicating that it was former News of the World newsdesk editor Greg Miskiw.