The Metropolitan Police's investigation into hacking has widened from allegations of voicemail interception to that of emails and computer files, Channel 4 News has learned.

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Scotland Yard has set up a new team to look into claims made by various individuals, including a man believed to be a former security agent, that their personal computers were hacked into in other ways than by voicemail interception.

Channel 4 News has seen a letter written on Wednesday by a Detective Inspector from Scotland Yard's Economic and Specialist crime directorate, to the lawyer of the Kevin Fulton - understood to have worked in the past as a British agent within the IRA.

Fulton wrote to the police in April alleging that some of his emails had been intercepted in 2006 by people acting on behalf of News International, publishers of News of the World, and sister titles, The Sun, The Times and the Sunday Times.

In response, the Metropolitan Police Service (MPS), wrote: "As a result of the new enquiry being conducted by the MPS into the unlawful interception of voicemail messages (Operation Weeting) and the various court actions relating to News International, the MPS has received a large number of enquiries and allegations relating to access to private data that are broader than voicemail interception...The MPS has set up a small team in order to assess the various allegations that have been made with a view to establishing whether there is available evidence and if it would be appropriate to conduct any further investigation into these activities."

The new operation is believed to be called Operation Tuleta, although it is unknown when it was initiated or how many officers are assigned to the unit.

The Metropolitan Police letter on the new operation.

In response to Mr Fulton's claims, News International said "we have seen no evidence to support these claims. If there is evidence we ask for it to be provided to us."

The news comes a day after the House of Commons heard claims that former prime minister Tony Blair and the Duchess of Cambridge were targeted by private detective Jonathan Rees.

Labour's Tom Watson told MPs on Wednesday: "The convicted private investigator Jonathan Rees, a contractor to News International, targeted former prime minister Tony Blair for covert surveillance, and at least one former home secretary."

He said: "The Metropolitan Police are in possession of paperwork detailing the dealings of criminal private investigator Jonathan Rees.

"It strongly suggests that, on behalf of News International, he was illegally targeting members of the royal family, senior politicians and high-level terrorist informers, yet the head of Operation Weeting (Scotland Yard's codename for its probe into phone hacking at the News of the World) has recently written to me to explain that this evidence may be outside the inquiry's terms of reference.

"I believe powerful forces are involved in a cover-up."

A Met police spokesman said: "(We) can confirm that since January 2011 the MPS (Metropolitan Police Service) has received a number of allegations regarding breach of privacy which fall outside the remit of Operation Weeting.

"These allegations are currently being considered."

News of the World owner News International rejected Mr Watson's claims.

A spokesman said: "It is well documented that Jonathan Rees and Southern Investigations worked for a whole variety of newspaper groups.

"With regards to Tom Watson's specific allegations, we believe these are wholly inaccurate. The Met Police, with whom we are co-operating fully in Operation Weeting, have not asked us for any information regarding Jonathan Rees.

Three News of the World journalists have been arrested since the Met reopened its inquiry into claims that staff hacked into the answerphone messages of celebrities and politicians.