In a story exclusive to The Guardian, it has been revealed that News International hired a private investigator to follow and film two lawyers representing victims of phone hacking.

Derek Webb is an investigator who was previously commissioned by the paper's former Royal Correspondent Clive Goodman. Now evidence has emerged that shows he was later hired to video Mark Lewis, who represents the family of Milly Dowler, and Charlotte Harris, who represented football agent Sky Andrew. Andrew's case lead to the resignation of Andy Coulson, David Cameron's former media advisor.

Gordon Taylor and Max Clifford, the first two people to bring legal action against News International for phone-hacking, were also individually represented by Lewis and Harris.

In January 2011, Webb was tasked with collecting evidence to suggest that Harris had been having an affair with a solicitor in Manchester - a man whom Harris did not know. A little less than a year earlier, he also followed Lewis' former wife, filming her at home in Manchester and with her daughter, for reasons that remain unknown.

Scotland Yard is in possession of emails that disclose the names of those News International Employees who were behind this particular surveillance operation - although these names have yet to be revealed.

There is evidence to suggest that the pair of lawyers were subject to other surveillance operations, which may have involved Harris and her two children being followed by other investigators, but the names of who authorised this activity are unknown.

Emails discovered by Scotland Yard also detail that News International solicitors threatened Lewis with an injunction should he take on anymore phone hacking clients. The solicitors failed to follow through on their threat when Lewis proceeded to do just that.

Tom Watson, a member of the Commons' culture select committee, told BBC NewsNight that James Murdoch has "got some very serious questions to answer" when he appears in the House of Commons for the second time on Thursday.

A News International spokesperson told The Guardian : "News International's enquiries have led the company to believe that Mark Lewis and Charlotte Harris were subject to surveillance. While surveillance is not illegal, it was clearly deeply inappropriate in these circumstances. This action was not condoned by any current executive at the company."

Source: The Guardian