Sky News admits to hacking emails, including the account of John Darwin, the "canoe man" accused of faking his own death.
A statement from John Ryley, the news channel's head, said that on two occasions it authorised a journalist to access the email of individuals suspected of criminal activity.
One occasion was the 2008 case of Anne Darwin, the wife of John Darwin, when she was due to stand trial for deception.
"Sky News met with Cleveland Police and provided them with emails offering new information relevant to Mrs Darwin’s defence," said Mr Ryley. "Material provided by Sky News was used in the successful prosecution and the police made clear after the trial that this information was pivotal to the case."
"We stand by these actions as editorially justified and in the public interest," Mr Ryley added. "We do not take such decisions lightly or frequently."
The statement went on to describe two separate investigations where tensions had arisen between the law and investigative journalism. It said these situations required "finely balanced judgement based on individual circumstances and must always be subjected to the proper editorial controls".
Sky's statement followed a report in the Guardian which alleged that the channel's northern correspondent Gerard Tubb had hacked emails during two investigations - including the interception of Mr Darwin's emails - and that both instances of hacking had been approved by Simon Cole, the managing editor of Sky News.
Please wait while this video loads. If it doesn't load after a few seconds you may need to have Adobe Flash installed.
The Guardian story claimed that no public interest defence can be used in this case because there is not one written in law that applies to the Computer Misuse Act: "Theoretically, however, any email hacking charges would have to be brought at the discretion of the police and the Crown Prosecution Service, which could weigh up whether any intrusions could be justified," the paper said.
"The role of the CPS in this area is untested, and Keir Starmer, the director of public prosecutions, told the Leveson inquiry in February that he intended to issue guidance to clarify the issue."
Cleveland Police have released a statement about the hacking allegations linked to the Darwin case. "Cleveland police has conducted an initial review into these matters and can confirm that enquiries are ongoing into how the emails were obtained."
In a separate statement published on its website Sky News accused the Guardian of double standards with the Guardian and its sister paper successfully justifying investigations where private data was obtained illegally using the a public interest defence.
The revelations come at a difficult time for Sky News following the resignation earlier this week of James Murdoch as chairman of BSkyB, Sky News's owner.
Mr Cole has since left the company. Following the Guardian's story he took to the social networking platform Twitter to deny that his departure was linked to the Darwin investigation.
"I've been planning for some time to retire from Sky News after 17 years," he said.
BSkyB shares fell on the London stock market after its admission, down 3.4% at the close to 652 pence.
Until now, broadcasters have been left relatively untainted by the hacking scandal. Unlike the press, the industry has a regulator - Ofcom.
Ofcom has been looking into whether News Corp, News International's owner, remains a "fit and proper" owner of BSkyB after two News International papers, The News of the World and the Sun were implicated in the phone hacking scandal. News International closed the News of the World as a result of the scandal.
News Corp is currently owns just over a third of BSkyB shares and is bidding to take over the remaining 61 per cent of the broadcaster that it does not now own.
There has been tension between the Murdochs' ambitions for their UK media operations and UK regulators for some time.
In 2009 James Murdoch gave the MacTaggart Lecture at the Edinburgh International Television Festival. Entitled 'The Absence of Trust', the speech included a fierce attack on the current system of broadcasting regulation in the UK, particularly criticising Ofcom's interventions in the market.
Mr Murdoch stated that a heavily regulated environment with a large public sector "crowds out the opportunity for profit, hinders the creation of new jobs, and dampens innovation in our sector".
But he went on to praise "the free part of the market" in broadcasting where he said success had been achieved by "a determined resistance to the constant efforts of the authorities to interfere".