Prosecutors are reviewing the case against a Cheam private investigator alleged to have tapped into the telephones of about 20 high-profile figures.

Keir Starmer, QC, the Director of Public Prosecutions, ordered an urgent examination of files on Glenn Mulcaire to ensure police had acted properly.

Mulcaire, 38, was jailed in January 2007 with the News of the World journalist Clive Goodman for unlawfully intercepting messages from princes Harry and William.

When police raided the office of his Nine Consultancy firm on the Kimpton industrial estate they found a “war room” brimming with data on people in the public eye.

Mulcaire, formerly of Alberta Avenue, Cheam, admitted tapping into the phones of the model Elle Macpherson, Simon Hughes MP and Max Clifford, the publicist.

But it has now been alleged that several more celebrity “targets” were on a hit list he was pursuing and that some were unaware about the threat to their privacy.

Mr Starmer said: “I have no reason to consider that there was anything inappropriate in the prosecutions that were undertaken in this case.

"I am taking this action to satisfy myself and assure the public that the appropriate actions were taken.”

The Metropolitan Police has refused to begin a renewed criminal inquiry into the phone-hacking affair, saying there is no new evidence of wrongdoing.

But the Independent Police Complaints Commission is facing mounting pressure to investigate whether appropriate action was taken with the material collected.

Chris Huhne, the Liberal Democrat media spokesman, said: “Only an independent inquiry can properly consider any possible neglect of duty by the Specialist Operations Department into the original investigation.

“Given the scale and scope of the allegations, the possibility that other journalists and investigators were involved must now be seriously considered."

News International, the publisher of the News of the World, said in a statement that an internal investigation had revealed no fresh cases of its journalists bugging phones.