Blair quitting now would be seen as an admission of guilt, Jowell says

One of Tony Blair's staunchest cabinet supporters says that if the Prime Minister were to quit now it would be seen as a "presumption of guilt" over the Scotland Yard inquiry into "cash for honours".

Tessa Jowell, the Culture Secretary said: "Just imagine if he were to say next week, 'OK I am off', there would be a presumption of guilt in the absence of any conclusion from this inquiry. That won't do anyone any good." Ms Jowell's message to Labour MPs on the BBC Radio 4 Sunday AM programme will be seen as a warning that if they succeed in pushing Mr Blair out, the image of sleaze will stick to the Labour Party.

With the Prime Minister struggling to fend off calls for an early resignation, cabinet supporters rallied round to buy him more time to achieve his ambition of being in office for more than 10 years. However, reaching the landmark on 2 May is looking increasingly difficult. He is widely expected to have to go if any of his aides are formally charged with perverting the course of justice. "A lot of chat has been going on between MPs over the weekend about this, and the message will be conveyed this week that Blair must go if anyone is charged," said a Labour source.

The prospect of charges being brought, once thought remote, became stronger at the weekend after it emerged that 10 files of evidence have been sent by Scotland Yard detectives to the Crown Prosecution Service.

Charles Clarke, the former home secretary, who quit after taking the blame for a Home Office debacle over foreign prisoners, said it would be "seriously irresponsible" for Mr Blair to quit in the middle of Labour's election campaigns for the Scottish Parliament, the Welsh Assembly and English local authorities.

Mr Clarke, a long-standing critic of Gordon Brown, said the Chancellor was likely to face a challenge for the leadership. Mr Clarke said he was unlikely to stand, but he did not rule himself out.

His remarks will fuel speculation at Westminster that the Blairites are still hopeful of persuading a committed moderniser to stand against Mr Brown. So far, the only challenge has come from the left by John McDonnell, leader of the Campaign Group of Labour MPs.

Other hurdles for Mr Blair include a Commons vote on his plan to replace the Trident nuclear missile system, on which he will face a growing Labour revolt; and his strategy for pulling troops out of Iraq which he is committed to announcing later this month when "Operation Sinbad" against insurgents in Basra is over.

The first test of backbench support since it became known he had been interviewed by police a second time will come tonight at the regular meeting of the Parliamentary Labour Party. It is unlikely there will be open criticism of Mr Blair but there is increasing concern about the damage that the investigation is causing.

An ICM poll yesterday showed that 56 per cent of the public want him to go now rather than wait for his planned summer departure

Jon Cruddas, a former No 10 aide, who is running for the deputy leadership, said it was time for Labour to "move on", but he did not set a deadline.

Patricia Hewitt, the Secretary of State for Health, said the sleaze inquiry had been damaging but she warned Labour MPs not to let Mr Blair be "hounded out" of office". "Of course, the whole issue of the investigation, the allegations that are being made, of course that is damaging," she said. "But that is not a reason for the Prime Minister to be bundled out of office. The Prime Minister is giving outstanding leadership."

Ms Hewitt said it was "rubbish" to suggest there was paralysis in the Civil Service or that Mr Blair was merely holding out for his 10th anniversary in office.

She told ITV1's The Sunday Edition: "Tony Blair is one of the most outstanding prime ministers our country's ever had." He should be allowed to make the decision on when to go "in his own time", she added.

Jacqui Smith, the Chief Whip, who is taking soundings from Labour backbench MPs, said "most people take the view that people are innocent until proven guilty". She added that it would be "undemocratic" for Mr Blair to be driven from office by an inquiry, adding: "He will choose the right time for the country, and for him, to go."

The Deputy Prime Minister John Prescott led support for Mr Blair at a weekend Labour policy forum, saying Mr Blair had demonstrated "inspired leadership", integrity and "courage under adversity".

Should he stay or should he go?

* Deputy leadership candidate Jon Cruddas on BBC Politics Show: "Ten years is an awfully long time to be Prime Minister of any one country ... But the page has turned, it's time to move on."

* Party chairman Hazel Blears on BBC Newsnight: "Inevitably, when you have this kind of thing going on for months and months, it does have a corrosive effect. It is damaging for politics because there is a corrosive cynicism around that I think is damaging for the country."

* Constitutional Affairs Minister Harriet Harman on BBC Question Time: "It has eroded trust and it's been an unfortunate, to say the least, situation."

* Former Labour leader Lord Kinnock of Bedwellty on BBC News 24's Straight Talk: "It's done damage to politics, and the political democratic process ...The damage to reputation, to trust ... will take years and a great deal of action to try and repair."

* Liberal Democrat leader Sir Menzies Campbell: "This is a prime minister treading water while his Cabinet moves on ... he should go sooner rather than later ."

* David Cameron, Conservative leader, Prime Minister's Question Time: "Why does he not accept what everyone knows - that it is now in the national interest for him to go?"