Cash for honours: Investigators warn No 10 that 'no one is above the law'

The arrest of the PM's gatekeeper has pitched politics against police. Marie Woolf reports

Police involved in the cash-for-honours inquiry believe they are the victims of an "orchestrated campaign of attack" by Blairite politicians, following the arrest of Ruth Turner, a close aide of the Prime Minister.

Amid fresh speculation that Tony Blair and his aides will face another round of police questions, the police have accused allies of the Prime Minister of trying to manipulate them over the inquiry. Sources close to the investigation say that a fresh file of police evidence was presented to the Crown Prosecution Service last week.

Scotland Yard has recently received expert advice about how to strengthen a prosecution case against senior Labour figures. They have been told by the CPS who should be asked fresh questions to strengthen the prosecution case.

Senior Labour figures warned yesterday that another new arrest or the prospect of charges could have catastrophic political consequences and hasten Mr Blair's departure from office.

The pressure on the Prime Minister intensified after the police let it be known that they are furious that a string of politicians, led by David Blunkett, the former home secretary, have criticised the police over the arrest of Ms Turner on suspicion of perverting the course of justice.

Len Duvall, the Labour politician who chairs the Metropolitan Police Authority, said in a thinly veiled attack that it was "inadvisable" for people to comment on their lines of inquiry, and warned them not to try to "manipulate or pressurise" officers. He added: "No one in this country is above the law."

Glen Smyth, chairman of the Metropolitan Police Federation, said the politicians' remarks were "particularly disturbing".

"There are many junior officers who will feel subliminally that their careers are being threatened, and that's wrong," he added. His comments follow criticism from a string of Blair allies over the arrest. Speaking on BBC Radio 4, David Blunkett, said: "As I said when this story started being investigated, we want thoroughness, not theatre."

Lord Puttnam, a friend and former employer of Ms Turner, accused detectives of "theatrics" and called on the police to "put up or shut up".

Tessa Jowell, the Culture Secretary, told The Independent on Sunday: "I am not in any way challenging the police inquiry, but I was rather baffled by why it was necessary to do it in that way. I know Ruth very well and she is a person of the utmost conscientiousness and integrity."

The Prime Minister's gatekeeper was escorted to the police station on Friday morning, where she was swabbed for DNA, fingerprinted and photographed. While the 36-year- old was being questioned for several hours by Scotland Yard detectives on suspicion of perverting the course of justice, police combed her flat for files and emails on the hard drive of her computer. They had software that let them recover deleted files.

The arrest has sent shockwaves through the Labour Party. Members fear that the cash-for- peerages affair - first revealed by this newspaper - has now got far too close for comfort to the Prime Minister and is causing serious political damage.

Amid talk that other No 10 aides - including Jonathan Powell, Mr Blair's chief of staff, and John McTernan, the head of political operations - could again be interviewed by the police, some MPs believe that Tony Blair's ever closer involvement in the affair is making him a political liability.

"If this gets any closer to Blair we are seriously going to be talking about an early leaving date," said one veteran Labour MP.

Ms Turner is the fourth figure in the cash-for-peerages affair to be arrested, following Lord Levy, the Prime Minister's personal fundraiser, Des Smith, the former head teacher, and Sir Christopher Evans, the biotech tycoon. But the manner of Ms Turner's arrest was far more dramatic than the others: she faced a dawn swoop at her home.

One source close to the police suggested Ms Turner was arrested at her home because the alternative - to knock on the front door of Downing Street in full view of the TV cameras - would have been more embarrassing. He added that people suspected of perverting the course of justice were usually subject to surprise arrests to stop them destroying evidence.

But this weekend, to escape the glare of publicity Ms Turner has, on the advice of No 10, moved out of her Westminster home to a safe house where she cannot be tracked down.

Friends of Ms Turner said it was ironic that a person known for her honesty and integrity - who made her name setting up a magazine for the homeless - had been arrested on suspicion of perverting justice.

Ms Turner set up the Big Issue of the North. She continued her work on social issues by founding Vision 21, a market research company for charities and the public sector. Organised and hard-working, Ms Turner first came to the notice of high-ranking politicians as a senior member of Labour students. She was then elected on to Labour's ruling National Executive Committee representing the party's grassroots. Although she has a wide circle of friends outside Downing Street and is a keen skier, she is said to "live for her work". Single, she once said that she had never aimed to work in politics, saying she "just fell in with the wrong crowd".

One colleague said that although Ms Turner was quiet she had an inner steeliness and that police tactics designed to intimidate her would not work.

So why was Ruth Turner arrested in so public a manner on suspicion of perverting the course of justice, which carries a maximum life sentence?

For months, Scotland Yard has been frustrated by holes in the evidence provided by Downing Street in the cash-for-honours affair. Police, who have downloaded files from Downing Street's hard drives, fear that emails have been deleted or have gone missing. They are also not convinced that government figures they have interviewed have been as open or helpful as they could have been - a charge that Downing Street vehemently disputes. During Friday's interview, Ms Turner is said to have been questioned about Sir Christopher Evans, who was not, in the end, offered a peerage but is believed in the past to have been considered as a suitable candidate because of his business and scientific achievements.

Friends of the tycoon say he has never had any contact with Ms Turner about peerages or any other matter and was never offered a peerage.

In the light of Ms Turner's arrest, the Government could be facing the particularly worrying prospect that Tony Blair could face a fresh police interview - this time not as a witness but under caution.

Last night, Lord Oakeshott of Seagrove Bay, a Liberal Democrat peer, said that the prospect of seeing Mr Blair in court, whether as a witness or defendant, was growing more likely.

"As Blair's right-hand woman, Ruth Turner can only have been acting on Blair's behalf," he said. "It is now looking even more likely that Mr Blair will have to tell the whole story in court."

The 'missing' email messages

The email trail relating to the award of honours to Labour's financial backers was not consistent. Police may have wanted to know if any emails were deleted or if records were erased before the inquiry. The Scotland Yard inquiry, led by Assistant Commissioner John Yates, right, is known to have trawled through Downing Street's hard drives.

The 'shredded' documents

The paper trail was not complete, with police fearing that records were either not being kept, or had even been destroyed. Downing Street has been criticised in the past for not keeping records.

The 'withheld' testimony

After hundreds of hours of evidence, the police have found inconsistencies in what they have been told. There may have been gaps in Ms Turner's earlier evidence, given under caution. She refutes this, but arresting her on suspicion of perverting the course of justice suggests that Scotland Yard believes she has not helped the police paint a full picture.