The broadcaster said the evidence it discovered was handed to police and used in the successful prosecution of Darwin’s wife Anne for insurance and pension fraud.
Darwin, 61, faked his own death in a canoeing accident in 2002 so his wife, 60, could claim hundreds of thousands of pounds from insurance policies and pension schemes.
Former Sky News managing editor Simon Cole agreed that North of England correspondent Gerard Tubb could hack into Darwin’s Yahoo! email account.
Mr Tubb uncovered messages which cast doubt on Mrs Darwin’s claim during her criminal trial that her “domineering” husband forced her to go through with the fraud plan.
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.
In a separate case, Mr Tubb was authorised to access the emails of a suspected paedophile and his wife, although this investigation did not result in any material being published or broadcast.
John Ryley, the head of Sky News, said in a statement yesterday: “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.
“On two occasions, we have authorised a journalist to access the email of individuals suspected of criminal activity. We stand by these actions as editorially justified and in the public interest.”
Cleveland Police said in a statement: “Cleveland Police has conducted an initial review into these matters and can confirm that inquiries are ongoing into how the emails were obtained.”
Sky News is part of BSkyB, which is 39 per cent owned by Rupert Murdoch’s News Corporation. Official figures released yesterday showed the closure of the News of the World and payouts to phone-hacking victims have already cost Mr Murdoch more than £79m.
News Group Newspapers, the subsidiary which also publishes The Sun, has also taken a £160m accounting write-off to cover the loss of publishing rights for the defunct Sunday tabloid.
The company has set aside £23.7m for phone-hacking claimants’ damages and legal fees, and £55.5m for costs relating to the News of the World’s closure, including redundancy payments and legal fees, accounts lodged with Companies House show.
Last night, it emerged the millionaire owner of Wasps rugby club is a suspect in Scotland Yard’s computer-hacking investigation.
Steve Hayes, 50, remains on bail after being arrested in Hertfordshire in February by detectives from Operation Tuleta, an offshoot of the force’s Weeting investigation into illegal activities at News International.