The management and standards committee (MSC) has been criticised by the National Union of Journalists for posing "a serious threat to press freedom" - and a Times report yesterday suggested that the MSC had revealed the identity of police officers, a civil servant and an army officer on the grounds that "they do not deserve protection [paywall]".
A person familiar with the MSC's work told Journalism.co.uk that the committee had a duty to help the police investigation - and that it was focusing specifically on payments to public officials that might be unlawful.
The source said: "We are deeply conscious of the obligation to protect sources and not to unwittingly hand over anything that would expose a perfectly regular, lawful source."
The source added that documents were being "redacted carefully" and that the committee received ongoing advice from a team of lawyers and external advisers.
The National Union of Journalists has expressed concern about the committee's work. General secretary Michelle Stanistreet said earlier this week: "We are receiving calls from whistle-blowers who had been assured that they would be protected, and who now fear for their jobs and worse."
News International's staff association, Nisa, is also reported to have written to News International management, seeking an urgent meeting with chief executive Tom Mockridge and reassurances that sources are not being compromised.