James Murdoch returns to Britain's parliament on Thursday for a second grilling over the phone hacking scandal in a showdown that could deepen the crisis in his father Rupert Murdoch's media empire.

Lawmakers have hauled back the News International chairman over apparent discrepancies in evidence he gave at a first hearing in July over the controversy that closed the News of the World tabloid.

Murdoch, 38, whose position as heir apparent to his father's News Corp. conglomerate has appeared increasingly shaky, claimed then that he had not seen a 2008 email suggesting that phone-hacking went beyond one reporter.

But his evidence was later challenged by two former senior executives at the tabloid, prompting parliament's culture, media and sport committee to recall him.

"I want to know the answers to a series of questions emanating from Murdoch's last appearance before the committee. What emails did James Murdoch really see?" said Labour committee member Steve Rotheram.

Damaging new claims in the past week have added to the pressure on James Murdoch, with allegations that a private detective hired by the News of the World tracked lawyers of hacking victims and a string of public figures.

News International, the British newspaper publishing arm of US-based News Corp., admitted last week the lawyers had been followed and said it was 'deeply inappropriate'.

On the eve of his appearance, the News of the World's former chief reporter, Neville Thurlbeck, also claimed that the paper did not act on information he gave it about hacking.

James Murdoch's position in News Corp. has appeared increasingly shaky and his performance could play a role in determining whether he is re-elected chairman of British pay TV-giant BSkyB at an AGM at the end of the month.

At an annual News Corp. shareholders' meeting in the US last month, he had to rely on the 40 per cent of votes controlled by the Murdoch family to win relection to the company's board.

In a first appearance alongside his father on July 19, James Murdoch maintained he was only aware that hacking was carried out by one 'rogue reporter', former royal editor Clive Goodman.

Goodman was jailed in 2007 along with private investigator Glenn Mulcaire after they admitted hacking into the phones of royal aides.

Murdoch claimed that he only learnt of allegations that other journalists were involved in 2010 when a series of celebrities launched legal action.

But his testimony was immediately contradicted by the paper's former legal chief, Tom Crone and former editor, Colin Myler.

The executives told lawmakers they informed Murdoch at a meeting on June 10, 2008, about an email apparently meant for chief reporter Thurlbeck which showed clear evidence that hacking went beyond one journalist.

The meeting was aimed at settling a hacking claim brought by Professional Footballers' Association chief executive Gordon Taylor and Murdoch subsequently authorised a substantial settlement for the football chief.

Documents released by News International's former lawyers Farrer and Co last week suggested there may have been an earlier meeting between Myler and James Murdoch around May 27, 2008 at which the email may have been discussed.

The phone-hacking scandal dogged News International, which published the News of the World, for several years but escalated into a full-blown crisis a few months ago when it emerged a murdered teenager's phone had been hacked.

The paper was closed in July and two of Rupert Murdoch's most trusted executives quit amid the subsequent storm, as well as Britain's top police officer and one of his deputies following criticism of the original probe.

The Murdochs' previous appearance in front of the parliamentary committee was disrupted when a man flung a foam pie into Rupert's face. Rupert's wife Wendi Deng then hit the assailant.