David Cameron under pressure to defend Coulson as calls for inquiry grow

Labour leadership rivals unite in call for inquiry as victims take case to High Court

David Cameron was under growing pressure last night to defend Andy Coulson, his director of communications, after lawyers, senior politicians and other public figures called for a full inquiry into allegations that the scale of the News of the World phone hacking scandal was much greater than police have acknowledged.

All five candidates for Labour's leadership used a debate yesterday to call into question Mr Cameron's judgement in appointing Mr Coulson, the former News of the World editor, to head his press machine. In a further development, lawyers for a group of public figures confirmed they were to go to court this week to force Scotland Yard to disclose the names of thousands of politicians, celebrities and journalists who are believed to be victims of phone hacking.

The scandal is now threatening to engulf the Prime Minister on the day that Parliament reopens – at a time when Mr Cameron would have been hoping to focus on a crucial debate over a proposed new voting system.

The High Court case will challenge the Metropolitan Police over its decision to limit the original investigation to just a handful of victims who had their phone messages intercepted by a private detective working for the News of the World. At the time Mr Coulson said he knew nothing about the paper's unlawful reliance on private detectives to hack into phone messages of celebrities, their agents, and members of the royal household.

The names of former Labour cabinet ministers John Prescott, Peter Mandelson and Tessa Jowell are among thousands of prominent people whose phone details were found when police raided the home of the private investigator Glenn Mulcaire, who was working for the News of the World when it was edited by Mr Coulson.

Asked about the phone hacking scandal during a leadership debate in Norwich yesterday, David Miliband, the frontrunner, said that anyone could be the target of hacking if it was allowed to go unchecked, and that governments should protect the privacy of individuals from intrusion by private organisations as well as by the state.

Ed Miliband described the allegations as "very serious", and Ed Balls added: "When there are questions about the integrity of the communications operation in Downing Street, the wrong thing for a Prime Minister to do is to try to sweep it under the carpet."

Andy Burnham said: "Mr Cameron has been delivering fairly pompous lectures for some time now about restoring trust in politics and the position Andy Coulson holds is fundamental to the information that the Government puts out. We just can't have a situation where these questions keep swirling around this individual. They need to be cleared up once and for all."

Mr Coulson resigned as editor after Clive Goodman and Mulcaire had pleaded guilty to illegal phone tapping, but has always denied that he knew about their activities. Leading Tories believe that the revival of the phone tapping scandal is simply down to rivalry between newspaper empires, and the issue has been seized on by politicians from opposition parties who want to embarrass Mr Cameron by attacking his chief spin doctor.

Interviewed on the BBC's Andrew Marr show yesterday, the Education Secretary Michael Gove claimed there was "no evidence" that Andy Coulson knew about the phone hacking while it was taking place. "There seems to be a recycling of allegations we have had before," he said. "It is striking that many of the people making allegations are Labour politicians, so there is an element of the party political about it."

But Paul Farrelly, a Labour MP involved in an inquiry by the Commons Culture Media and Sport Select Committee in September last year accused the police of being "less than fulsome" when answering MPs' questions.

He added: "With Andy Coulson our inquiry hit a brick wall of silence and amnesia. There is plenty more in a New York Times article, however, which suggests illegal phone-hacking was rife and not limited to just the former royal editor and one private investigator. We concluded in our report that this was unbelievable."

Later this week the former Europe minister Chris Bryant, former Metropolitan police deputy assistant commissioner Brian Paddick, and journalist and author Brendan Montague are expected to issue proceedings for judicial review against Scotland Yard.

Their solicitor Tamsin Allen, of London law firm Bindmans, told The Independent that the police had a duty under the Human Rights Act to protect the public's privacy and to pass on any information that might indicate they were the victims of hacking.

Ms Allen insisted that the legal action was not politically motivated and that she represented clients who were only interested in establishing the truth about the original police investigation and what decisions were taken regarding the use of personal information.

Scotland Yard has confirmed that there are 4,332 "names, partial names and initials" amongst documents seized from Glenn Mulcaire and Clive Goodman.

The list of names is also the focus of a separate court battle involving Scotland Yard in which the police are accused of defamation. In that case solicitor Mark Lewis, who acted for Gordon Taylor, the chief executive of the Professional Footballers' Association, is suing the Metropolitan Police over claims that he misquoted a detective when he gave evidence to the Commons committee last year.

Mr Lewis told the committee that he had been told by Det Sgt Mark Maberly – who has since been promoted to Detective Inspector – that there was evidence that about 6,000 hacks had taken place. He added that it was not clear to him whether this meant that 6,000 phones were hacked or that 6,000 people, including those who had left messages, were affected.

He is also suing the Press Complaints Commission and its chairman Baroness Buscombe over a speech she made at the Society of Editors conference in November last year in which she said that Mr Maberly was wrongly quoted, and that the Metropolitan Police had said the correct figure – only a handful – was given to the Select Committee by Assistant Commissioner John Yates and Detective Chief Superintendent Philip Williams.

Mr Lewis claims that these statements amount to allegations that he lied to the Select Committee.

A spokesman for the Met said: "In July 2009, the MPS examined whether any new evidence had emerged in the media or elsewhere that justified reopening the investigation. The clear view, subsequently endorsed by the Director of Public Prosecutions with leading counsel's advice, was that there was no new evidence and consequently the investigation remains closed. There has been no investigation since the convictions of Goodman and Mulcaire."