The head of Sky News said journalists have to consider breaking the law to "shed light" on wrongdoing as it emerged that media regulator Ofcom is launching an investigation into the hacking of private email accounts by the broadcaster.
Ofcom announced the investigation after the news channel admitted it had accessed the accounts of back-from-the-dead canoeist John Darwin and his wife Anne, as well as those of a paedophile. The watchdog said it is investigating the "fairness and privacy issues" raised by the hacking.
John Ryley, head of Sky News, told the Leveson Inquiry into press standards that occasions where a journalist would break the law in pursuit of a story would be "very, very rare".
"Journalism is at times a tough business," he said. "And we need at times to shed light into wrongdoing. There may be an occasion. It would be very, very rare."
Darwin, 61, faked his own death in a canoeing accident in 2002 so his wife could claim hundreds of thousands of pounds from insurance policies and pension schemes. The Darwins, from Seaton Carew, near Hartlepool, were jailed at Teesside Crown Court in 2008 for the swindle, which deceived the police, a coroner, financial institutions and even their sons, Mark and Anthony.
The broadcaster said evidence discovered by north of England correspondent Gerard Tubb was handed to police and used in the successful prosecution of Mrs Darwin, 60, for insurance and pension fraud.
The inquiry heard how Mr Tubb learned from a "source close to the prosecution" that an email account used by Mr Darwin was not going to be used as evidence.
Mr Ryley said Mr Tubb had accessed the account in June 2008 while working on a "court backgrounder" to be broadcast at the conclusion of the trial. "He had been working on it for five to six months," Mr Ryley said.
Ten days after accessing the account, the findings were reported to the police. The detail was "pivotal" in the case against the fraudsters, the inquiry heard.
A Ofcom spokesman: "Ofcom is investigating the fairness and privacy issues raised by Sky News' statement that it had accessed without prior authorisation private email accounts during the course of its news investigations. We will make the outcome known in due course."