Rupert Murdoch's News Corporation is still facing the threat of legal action from its own journalists despite the mogul's attempt to rally the troops at his News International UK newspaper group. The National Union of Journalists was on Friday determined to pursue a potential human rights challenge to the News Corp unit that is disclosing journalists' confidential sources to the police. One NUJ insider said that legal discussions with two leading QCs, John Hendy and Geoffrey Robertson, were ongoing and that they were examining the possibility of a group legal action against News Corp's management and standards committee. On Friday afternoon Murdoch toured the Sun's Wapping newsroom in east London in an attempt to quell the disquiet among some of his most senior journalists. The chairman and chief executive of News Corp, News International's US parent company, immediately lifted spirits when he pledged his "unwavering" commitment to the Sun and announced the launch of the Sun on Sunday "very soon". However, Murdoch also stood by News Corp's MSC, saying the unit would continue to "turn over every piece of evidence we find". Murdoch said in a memo to News International staff: "Our independently chaired management and standards committee, which operates outside of News International, has been instructed to co-operate with the police. We will turn over every piece of evidence we find – not just because we are obligated to but because it is the right thing to do." He said the Sun journalists arrested could return to work, but added: "We will continue to ensure that all appropriate steps are taken to protect legitimate journalistic privilege and sources, which I know are essential for all of you to do your jobs. But we cannot protect people who have paid public officials." On Friday afternoon the News International Staff Association indicated that its concerns had not been allayed by Murdoch's memo. "There are still some areas of understanding and clarification to be pursued on the role and actions of the MSC," the staff association said.Robertson said Murdoch's letter to staff "is full of errors" and News International was under no obligation to hand over evidence to police as journalistic material was protected by law. "Murdoch's letter to staff is full of errors, both of law and history. Apparently, he thinks it is right to hand over confidential source material – including the names of whistleblowers – to police without them even asking. This is a breach of the most fundamental ethic that journalists must not betray their source and there is no law that requires it. On the contrary, the 1984 Police and Criminal Evidence Act defines confidential journalistic material as 'excluded material' which police cannot seize at all, other than in a few cases such as official secrets, when they have to get an order from a circuit judge. So Murdoch, ill-advisedly and unethically is throwing away the shield that parliament gave to journalists in 1984 so they could protect their sources. "He also seems under the illusion that it's a crime to pay a source. It is an offence, certainly, to bribe or corrupt a public official but they can be paid for lunch, for travel expenses, for consultation time or legal costs, without any question of bribery arising. What is so unattractive about Murdoch's behaviour is that he is handing over journalists without ever asking them, or their editors, or their executives who must have signed off on the payments, what they were doing and whether they were genuinely pursuing a public interest story. Any significant payment must have been approved by executives, and News Corp does not appear to have turned them over. "But the real danger of this behaviour is that it is a blow to investigative journalism, which depends on the cultivation of sources. Whistleblowers will be much less likely to come forward, however much they trust the journalist, if they fear that his proprietor may turn them over to police. "Everyone seems to have forgotten that over 200 years ago John Wilkes went to prison to stop government agents getting hold of his journalistic material without a specific warrant. He sued the government and won a great constitutional case. He would be turning in his grave."