Four former executives from News Corp's UK newspaper arm will appear before a powerful parliamentary committee on Tuesday in the ongoing hunt to establish who knew what about phone hacking and whether James Murdoch did enough to uncover the scandal.

The committee called the four men who no longer work for News International -- two lawyers, the head of human resources and an editor -- after evidence emerged which suggested that the company had engaged in a huge corporate cover up.

The four will appear before the Culture, Media and Sport Committee to answer questions on their role in the hacking affair, which wiped billions off Rupert Murdoch's company in July as a sense of crisis engulfed the firm.

Their testimony is likely to increase pressure on James Murdoch as two of the men have already contradicted Rupert's son over what he knew and when, while another has accused both Murdochs of serious inaccuracies.

It's getting very interesting, Claire Enders, of the Enders Analysis media consultancy, told Reuters. Some of these senior ex employees have recently made statements which appear to go against what they had previously told the committee. And the committee are going after it now with some enthusiasm.

News International had long argued that the hacking of a few phones owned by celebrities was carried out by one 'rogue' reporter, Clive Goodman, who went to jail for the crime in 2007 along with a private detective, Glenn Mulcaire.

That position crumbled however as it became clear that the hacking of phones had been employed on an almost industrial scale and was used to secure stories not just on celebrities, but also murder victims and those killed in war.

In August, the committee released a private 2007 letter written by Goodman to News International, stating that phone hacking was widely known about and openly referred to at the paper, before the-then editor Andy Coulson banned any reference to it.

The letter had been sent to Daniel Cloke, the head of human resources, Les Hinton, the head of News International at the time, and a third executive.

As well as being asked to explain why this letter did not prompt a more thorough investigation, Crone will also likely be asked to elaborate on an earlier statement he made with Colin Myler, the editor at the paper when it closed, which contradicted evidence given by James Murdoch.

The two men said they had shown James Murdoch a damning email in 2008 which included the transcript of phone messages and which showed the involvement of two other journalists at the paper, showing it was more widespread than previously thought.

James Murdoch denies having seen the email and says he did not become aware of the scale of the problem until much later.

The fourth person to testify on Tuesday -- along with Crone, Myler and Cloke -- will be the head of legal affairs for commercial for News International, Jon Chapman, who has also questioned the Murdoch's insistence that they tried to get to the bottom of the problem.

James Murdoch has said he was satisfied by three early investigations which all cleared the company -- one by the police, one by the Press Complaints Commission (PCC) and the third by a law firm which looked at the issue as part of an unfair dismissal case for the jailed journalist Goodman.

The police have since said however that the paper was uncooperative, the PCC said it relied on inaccurate information provided by the company and the law firm complained that its work was never intended to be used for such purposes.

The committee has said it is likely to recall James Murdoch for further questioning.

(Editing by Myra MacDonald)

United kingdom Hacking