Tony Blair was rocked last night by a new crisis over Iraq after it was revealed that Ministers were told to ‘burn’ a secret document which said the war was illegal.

The Mail on Sunday has learned how Downing Street descended into panic on the eve of the war when Attorney General Lord Goldsmith told Mr Blair the conflict could be challenged under international law.

The Prime Minister was horrified, and Ministers and officials who had a copy of Goldsmith’s written opinion were told: ‘Burn it. Destroy it.’

Ten days later, with the invasion just days away, Goldsmith did a U-turn and said an attack could be justified. Among those who were told to ‘burn’ their copy was Defence Secretary Geoff Hoon, who flatly ignored the order.

Going to war: Former Prime Minister Tony Blair and ex-President George Bush shake hands in April 2002, at the Crawford summit where they are suspected to have signed a 'deal in blood' to wage war on Iraq

It is also claimed that Mr Hoon threatened to expose such Iraq War secrets when he resisted a bid by Tony Blair to kick him out of the Cabinet. Mr Hoon denied those claims last night. The disclosure is one of the most shocking indications yet that Blair and his inner circle were intent on war, while publicly claiming to be pursuing a diplomatic solution.

It has long been suspected that Labour’s ruling clique put pressure on the Attorney General to come up with a legal opinion in favour of the conflict – an accusation which is being investigated by Sir John Chilcot as a key part of his long-delayed inquiry into the war.

Last week, Sir John announced his report would not be published until June or July 2016.

David Cameron said he was ‘immensely frustrated’ at the length the inquiry, which began in 2009, while Labour leader Jeremy Corbyn said the time taken was ‘getting beyond ridiculous’.

The ‘burning’ row relates to the 13-page legal opinion presented by Lord Goldsmith to Mr Blair on March 7, 2003, less than three weeks before the outbreak of war.

The opinion – details of which were exclusively revealed by The Mail on Sunday in 2005 – stated that the war was likely to be challenged under international law because of the lack of backing from the UN.

The advice was never released and was kept secret from most of the Cabinet. Only a few powerful aides, such as No 10 director of communications Alastair Campbell, were allowed to see it. Even Chancellor Gordon Brown and Home Secretary David Blunkett were left out of the loop.

A senior No 10 figure at the time told The Mail on Sunday last night: ‘There was pandemonium. The date when war was expected to start was already in the diary, and here was Goldsmith saying it could be challenged under international law. They said “burn it, destroy it” and got to work on the AG [Attorney General].’

Lord Goldsmith’s one-page legal opinion, produced ten days later – and three days before war broke out – stripped out all of his previous reservations and declared the war to be legal. This version was discussed in Cabinet and cited in Parliament to justify military action.

Last night, a source close to Mr Hoon declined to identify the figure who issued the “burn it” order, except to say it was ‘not Tony Blair himself’.

The source said: ‘Geoff received the “burn it” order second-hand. He did not regard it as an instruction to be followed. Downing Street was very keen at the time that the document should not have wide circulation, but Geoff would argue that the remark should not be interpreted as a sign that they were determined to get the Attorney General to rewrite the advice.

‘Peter [Goldsmith] did say in that original advice that as long as certain conditions were satisfied then war was legal, but it did not give an absolutely clear view which could be used by the military. The later summary was much clearer.’

Refusal: Attorney General Lord Goldsmith (left) told Mr Blair the conflict could be challenged under international war, before doing a U-turn 10 days later. Among those who were told to ‘burn’ their copy of the Attorney General's report was Defence Secretary Geoff Hoon (right), who flatly ignored the order

The No 10 figure also claimed that when Mr Blair sacked Mr Hoon from the Cabinet in a reshuffle in May 2006, Mr Hoon raised the ‘burn it’ remark – something Mr Hoon denies.

Mr Hoon was furious to be moved by Mr Blair to the non-Cabinet position of Europe Minister – only for Mr Blair to later give him the right to attend Cabinet. It was speculated at the time that the concession was made because Mr Hoon ‘knows where the Iraq bodies are buried’.

There was pandemonium. The date when war was expected to start was already in the diary, and here was Goldsmith saying it could be challenged under international law. They said “burn it, destroy it” and got to work on the AG [Attorney General]. A senior No 10 figure at the time

Mr Hoon was one of Blair’s most loyal Ministers during the Iraq War, privy to secret intelligence and involved in the rows about legal advice. A confidential memo written by the US Embassy in London in 2002, which The Mail on Sunday revealed last month, described Mr Hoon and Foreign Secretary Jack Straw as the only Cabinet Ministers who were giving Mr Blair unqualified backing over his Iraq strategy.

Mr Hoon stood shoulder-to-shoulder with Mr Blair during the furore over the death of Government scientist Dr David Kelly, who was the source of a BBC report questioning the ‘dodgy dossier’ into Iraq’s alleged Weapons of Mass Destruction. The Defence Secretary was accused of neglecting his duty of care towards Dr Kelly, an MoD employee, by sanctioning the release of his name to the media.

Mr Hoon has admitted that he could have done more to help the scientist, but was cleared of wrongdoing by the Hutton report into Dr Kelly’s death.

In May 2005, the Cambridge-educated barrister, nicknamed ‘Buff Hoon’ at Westminster, was moved from Defence Secretary to Leader of the House, still a Cabinet position. A year later he was demoted to Europe Minister, taking a £35,000 pay cut. But even though this meant he no longer held a Cabinet post, he still continued to attend meetings in his usual seat next to Deputy Prime Minister John Prescott – a decision long surrounded in mystery.

Respected Labour chronicler Andrew Rawnsley wrote in his book The End Of The Party that Mr Hoon was initially so furious about his demotion that he wrote out a resignation statement and planned to make a speech about the Iraq War, including the death of Dr Kelly, which he told friends ‘could trigger the instant downfall of the Prime Minister’. In the event he remained quiet.

HOW BULLYING BLAIR AND HIS CRONIES MANIPULATED LEGAL ADVICE TO JUSTIFY THE WAR PLOTTED AT 'DEAL IN BLOOD' SUMMIT War 'not justified': Attorney General Lord Goldsmith 1. Bush and Blair meet – and seal Iraq's fate APRIL 2002: Tony Blair and George Bush meet at Crawford, Texas, where they are suspected to have signed a 'deal in blood' to wage war on Iraq. In a memo revealed by The Mail on Sunday last month, Secretary of State Colin Powell tells Bush that 'Blair will be with us' on military action.

2. Attorney General says war 'not justified' JULY 2002: Attorney General Lord Goldsmith sends a note to Blair on a single side of A4 headed notepaper saying why he thinks war could not be justified purely on the grounds of 'regime change'. He also says that although United Nations rules permit military intervention for self-defence, they did not apply in this case because Britain is not under threat from Iraq. And he says it would be very difficult to rely on old UN resolutions approving the use of force against Saddam Hussein.

3. Goldsmith silenced as clique takes control SUMMER 2002: Blair issues instructions to gag Goldsmith, banning him from attending Cabinet and ordering a cover-up to stop the public finding out the contents of the letter. Goldsmith threatens to resign, but Blair and his cronies bully him into backing down.

4. Goldsmith AGAIN says conflict may be illegal MARCH 7, 2003: Goldsmith produces a 13-page document stating that the war could be challenged under international law. One argument is that individual nations cannot decide if Iraq is in 'material breach' of UN resolutions on disarmament. He also urges caution about going to war without a second UN resolution: 5. U-turn on legal advice clears the way for action MARCH 17, 2003: Goldsmith gives a nine-paragraph Parliamentary answer summarising his advice, declaring war to be legal under existing resolutions: 6. Britain goes to war MARCH 20, 2003: Baghdad is hit by air strikes and Coalition forces on standby in Kuwait invade. Advertisement

Despite the Cabinet concession, Mr Hoon started plotting against Blair almost immediately after his demotion. In September 2006, he called on Blair to stand down in favour of Gordon Brown before the 2007 local elections.

Last night, leading international lawyer Professor Philippe Sands QC, of University College London – who eviscerated the Blair Government for its role in the last-minute change of legal advice in his book Lawless World – said: ‘I wouldn’t be surprised in the least about an order to “burn” the advice.

The problem was it had already been distributed more widely, and thankfully so, or we wouldn’t ever have known about the abrupt and unhappy U-turn and the circumstances in which it was procured.’

When contacted by The Mail on Sunday, Mr Hoon, 61, said: ‘I will not be making any comment while the Chilcot Inquiry is still under way, but the remark in question did not come up during my job negotiations with Tony Blair in 2006.’

SIX YEARS TO SEE A MEMO... AND IT'S ALL WHITEWASHED Confidential communications between Tony Blair and George Bush in the run-up to the Iraq invasion have been released after a six-year battle – but nearly all of the pages have been left blank. American officials have finally released 13 pages of heavily censored documents in response to a Freedom of Information request made by The Mail on Sunday in August 2009. But the US State Department removed virtually all the information from the papers, rendering them meaningless and reinforcing fears of a cover-up. Maurice Frankel, director of the London-based Campaign for Freedom of Information, said: ‘It’s been a long wait for next to nothing. The Americans don’t want to risk embarrassing their allies.’ When the State Department finally replied to our 2009 request on October 21, it identified 16 documents, but withheld five over ‘national security’ issues and released another two with what it called ‘excisions’. Incredibly, it said it needed even more time to consider the fate of the remaining documents. Of the 13 pages released, four are little more than blank pages save for the word ‘Unclassified’. The documents from 2003 point to a flurry of memos between the US Embassy in London and Washington prior to a meeting between Blair and Bush at Camp David. Although subject headings have been declassified, the substance has not been included – as the large white spaces on the released document, right, show. American public bodies are supposed to process Freedom Of Information requests within 20 days. The State Department did not explain why this case took so long. It added that ‘redaction criteria include national security, personal privacy, and trade secrets’. Advertisement

A spokesman for Mr Blair said: ‘This is nonsense as far as Tony Blair knows. No one ever said that in his presence and in any event it would be quite absurd to think that anyone could destroy any such document. Mr Blair and Lord Goldsmith dealt with all the circumstances surrounding the advice at the inquiry at length and with all the documents. The fact is that the advice given was that the action was legal and it was given for perfectly good reasons.’

The spokesman added that Mr Blair had made it clear to the Chilcot Inquiry that the UK would not have participated in the decision to remove Saddam if Lord Goldsmith had not ‘finally been of the view’ that the war was legal.