Media regulator Ofcom is to investigate Sky News over its admission that one of its journalists hacked into the private email account of "canoe man" John Darwin and his wife Anne.
Earlier this month the broadcaster said it stood by its decision after ruling the action was in the public interest.
Sky News 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.
A spokesman for Ofcom today told Press Gazette the investigation was self-initiated and that is had not received a complaint from any of the parties involved.
It is expected to report on its findings within 90 working days.
In a statement the regulator said: "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."
Darwin, 61, faked his own death in a canoeing accident in 2002 so that his wife could claim hundreds of thousands of pounds from insurance policies and pension schemes.
On 5 April Sky News confirmed that former managing editor Simon Cole agreed that North of England correspondent Gerard Tubb could hack into Darwin's Yahoo! email account.
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.
In a separate case Tubb was also 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 who is due to appear at the Leveson Inquiry today, said at the time: "We stand by these actions as editorially justified and in the public interest. We do not take such decisions lightly or frequently.
"They require finely balanced judgment based on individual circumstances and must always be subjected to the proper editorial controls."
The Darwins were jailed at Teesside Crown Court in 2008.
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