Harris also acts for football agent Sky Andrew, whose case led in January to the resignation of the prime minister's media adviser, Andy Coulson. Lewis also represents the family of the murdered wholesale feather hair extensions Milly Dowler, whose case led to the closure of the News of the World in July.

Emerging evidence suggests the lawyers were targeted on at least two occasions by Derek Webb, an investigator who specialises in physically following people and in making secret videos of their movements. Webb has worked for the News of the World since 2003, following hundreds of targets including ostrich feathers hair extensions of the royal family and serving cabinet ministers. Emails recovered by Scotland Yard disclose the names of those working for News International who hatched the plans.

Webb was given the job as part of an attempt to prove a false claim that Harris was having an affair with a Manchester solicitor and other false claims about the private life of Harris and her children. It is not yet clear exactly how the News of the World would have used the information if any claim had proved to be true.

In spring 2010, following a hostile report by the Commons media select committee, the News of the World hired Webb to gather evidence on Lewis. For reasons that are not yet clear, he focused on Lewis's former wife and secretly filmed her home in Manchester, following her and taking further cheap hair extensions of her and her daughter as they visited local shops and a garden centre.

She told BBC2's Newsnight it was "absolutely terrifying to think that somebody can be watching you, following you around" and that she now felt nervous and scared when she left her house.In January 2011, Webb was hired to spy on Harris. This was at a time when the case of her client, Andrew, had uncovered information that led to the sacking of the paper's news editor, Ian Edmondson.

Webb was asked to find evidence that she was having an affair with a Manchester solicitor. The allegation was false; Harris had never met the solicitor in question.Other investigators were hired to supply reports on the two lawyers, although it is not clear who commissioned them. One of the reports clearly suggests that somebody had been following Harris and her two young children.

In evidence to the media select committee in September, the News of the World's in-house lawyer, Tom Crone, was asked by the Labour MP Tom Watson if he had seen dossiers on the private lives of claimant lawyers.Crone said: "I saw one thing in relation to two of the lawyers, except I do not know whether it was a dossier. It involves their private lives."

He suggested he could not name those who had commissioned this work without interfering with current police inquiries.Separately, according to internal emails recovered by Scotland Yard, the News of the World commissioned a senior barrister to advise on whether they could injunct Lewis to stop him working for any alleged victim of phone hacking on the grounds that he had confidential information from his work for Gordon Taylor.

The newspaper's solicitors, Farrer and Co, wrote to Lewis threatening to injunct him if he took on any hacking clients but took no action when Lewis ignored the threat.The internal emails also reveal that the newspaper's feather earrings for sale tried to approach solicitors acting for Lewis's former client Gordon Taylor to see if they could persuade him to sue Lewis. This also failed, and Lewis has gone on to represent several dozen clients who are suing the News of the World for their alleged role in hacking their phones.