The ex-Labour minister said his own adviser was told “in no uncertain terms” to get rid of a memo written by former attorney general Lord Goldsmith.
Details of Mr Hoon’s claims, which appear in his recently-published memoir See How They Run, comes as the former prime minister faces a campaign to block his knighthood.
More than 680,000 people have signed a petition to rescind the gong, and a YouGov poll indicated that 63 per cent of Britons are against the move to turn Mr Blair into Sir Tony.
Mr Hoon claimed the order to burn the legal memo came from Jonathan Powell, Sir Tony’s then-chief of staff at No 10, according to details published in the Daily Mail. Mr Powell denies the allegation.
The former Labour minister said he was sent a copy of Lord Goldsmith’s memo “under conditions of considerable secrecy” and told he should “not discuss its contents with anyone else”.
He wrote: “I read the opinion several times; it was not an easy read. Eventually I came to the view that the attorney general had decided that invading Iraq would be lawful if the Prime Minister believed that it was in the UK’s national interest to do so. It was not exactly the ringing endorsement that the Chief of the Defence Staff was looking for, and in any event, I was not strictly allowed to show it to him or even discuss it with him.”
Mr Hoon added: “Moreover, when my Principal Private Secretary, Peter Watkins, called Jonathan Powell in Downing St and asked what he should now do with the document, he was told in no uncertain terms that he should ‘burn it’.”
The former defence secretary said he and principal private secretary decided the memo should be locked in a safe at the Ministry of Defence rather than destroy it.
Sir Tony’s office described the allegation that the memo was ordered to be burned as “nonsense” when it first emerged in 2015.
Mr Powell denied telling Mr Hoon to burn the memo. He told the Daily Mail that Mr Hoon had been sent copies of a separate “minute” on the legality of the invasion months earlier. He had asked Mr Hoon, at the request of Lord Goldsmith, to “destroy the minute – not burn it – and the attorney general’s advice came later”.
Human rights lawyer and academic Philippe Sands said Mr Hoon’s claims offered “further confirmation of what has long been known – ministers, parliament and the public were misled by Mr Blair into supporting a war that was seen by many as unlawful and a crime”.
He added: “In modern Britain, it seems, such a manifest act of wrongdoing does not preclude the offering of a high-level gong.”
Labour leader Sir Keir Starmer came out in support of Sir Tony’s knighthood on Tuesday, saying: “I think he deserves the honour.”
Questioned about the strength of feeling about the Blair government’s invasion of Iraq, Sir Keir said: “I understand there are strong views on the Iraq war, there were back at the time and there still are.”
He added: “But that does not detract from the fact that Tony Blair was a very successful prime minister of this country and made a huge difference to the lives of millions of people in this country.”
The Independent has contacted the office of Tony Blair and the office of Jonathan Powell for comment.
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