James Murdoch rejected allegations on Thursday that he was a 'mafia boss' and told British lawmakers he had not misled them about the extent of his knowledge of phone-hacking at the News of the World.

In heated exchanges after being recalled for a second grilling by MPs, the News International chairman repeatedly denied he knew in 2008 about a smoking-gun email that suggested hacking at the tabloid was endemic.

He sought instead to shift the blame onto the now-defunct paper's former legal chief and ex-editor, who had accused the 38-year-old of lying when he and his father Rupert testified to a parliamentary committee in July.

At Thursday's appearance, lawmakers led by anti-hacking campaigner and opposition Labour politician Tom Watson grilled James Murdoch about a meeting he had with former editor Colin Myler and legal exec Tom Crone.

"Mr Murdoch, you must be the first mafia boss in history who did not know he was running a criminal enterprise," said Watson.

"Mr Watson, please," said Murdoch, apparently taken aback.

Security was tight for the hearing, after the Murdochs' previous appearance was disrupted when a man flung a foam pie into Rupert's face.

The apparent discrepancy in James Murdoch's evidence focused on a meeting in June 2008, when he met Crone and Myler.

On Thursday he admitted that at the meeting, which was aimed at deciding a payout for hacking victim Gordon Taylor, head of the Professional Footballers' Association, he was told of the email.

But he denied ever being shown the so-called 'for Neville' message - which contained hacking transcripts and was apparently meant for the paper's chief reporter Neville Thurlbeck - or realising it indicated hacking was widespread.

"The nature of the 'for Neville' email... any suspicion of wider-spread wrongdoing, none of these things were mentioned to me," he told lawmakers.

He said Myler and Crone had 'misled' parliament.

Murdoch also repeated his apologies for the scandal which led to the closure of the News of the World in July after 168 years.

"The whole company is humbled by this... We are all humbled by it and trying to improve the business, improve the structures and leadership," he said.

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 Rupert Murdoch's US-based News Corp media empire, admitted last week the lawyers had been followed and said it was 'deeply inappropriate'.

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.

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.