Sky News, a part of Rupert Murdoch's media empire, has admitted to hacking into emails on two occasions, terming their action editorially justified and in the public interest.
On one occasion, the news channel of BSkyB, the British broadcaster, authorised a journalist to access the emails of a man accused in 2008 of faking his own death, the head of Sky News, John Ryley, said in a statement on Thursday.
"Material provided by Sky News was used in the successful prosecution [of the case] and the police made clear after the trial that this information was pivotal to the case," the statement said.
The case of Anne and John Darwin became notorious in Britain in 2008 after the latter faked his own death in a boating accident as part of an elaborate insurance scam.
In a separate investigation, the broadcaster said, a Sky News journalist purchased a machine gun in 2004, while reporting on the easy availability of illegal weapons in the UK.
Sky said it also once authorised a reporter to penetrate airside security at London's Heathrow airport in 2003, as part of an investigation into the failings of the facility's security systems.
"Sky News is committed to the highest editorial standards. Like other news organisations, we are acutely aware of the tensions that can arise between the law and responsible investigative journalism," Ryley said.
"We stand by these actions as editorially justified and in the public interest."
Some legal experts have said that the "public interest" defence may not stand up in court.
David Allen Green, a London-baed media lawyer, said that there was no such thing as a public interest defence as far as Britain's Computer Misuse Act was concerned.
"It is not possible for the editor of any news organization to authorise criminal acts," said Green, who has been a frequent critic Murdoch's News Corporation.
News Corporationis the biggest shareholder in BSkyB, holding a 39 per cent stake.
BSkyB is currently being investigated by Britain's broadcasting regulator as to whether its executives and owners make it a "fit and proper" owner of a broadcast licence.
The company says that it has commissioned an external review of email records at Sky News, as well as an internal audit of payment records.
Ryley said that while the email review is still underway, "no grounds for concern have been found" so far.
Shares in BSkyB, which had been trading 0.3 percent higher at 12:30 GMT on Thursday, were down 4.1 per cent at 631 pence by 12:57 GMT, making them the biggest faller on Britain's FTSE-100 index.