TONY Blair faces “damage” to his reputation in the forthcoming Chilcot inquiry report into the war in Iraq as the £10 million probe delivers an “absolutely brutal” verdict on the mismanagement of Britain’s role in the invasion and occupation, according to a senior source.

The former minister, who is said to have discussed the report with two of its authors, has made clear the former Prime Minister “won’t be let off the hook” over claims that he offered British military support to George W Bush, the then US President, a year before the 2003 invasion.

Jack Straw, the former Foreign Secretary, and Sir Richard Dearlove, who headed MI6, are also set to be censured when the report is published on July 6, seven years after the inquiry began.

Security chiefs are set to be criticised for failing to prevent Downing Street from putting a “gloss” on the intelligence surrounding Saddam Hussein’s weapons of mass destruction, which led to the claim in the so-called “dodgy dossier” that the former Iraqi leader could attack UK targets within 45 minutes.

A former UK Government insider with knowledge of the Chilcot inquiry’s deliberations said: “It will be absolutely brutal for Straw. The build-up to war is very crucial. It will damage the reputations of a number of people, Richard Dearlove as well as Tony Blair and others. But there is a second half. The report will say that we really did make a mess of the aftermath.”

Mr Straw is expected to come under heavy criticism over the quality of Foreign Office staff sent to run the civilian administration in Iraq and the lack of resources given to them.

“We sent in inexperienced people. People were put in positions where they couldn’t succeed. We didn’t quite know what we were doing. After the invasion we found it very much more difficult than we had expected,”said the source.

The section on Britain’s withdrawal from Basra in 2007 is said to be “embarrassing”.

The report is believed to conclude that the UK cabinet did not have “the full picture” of developments ahead of the invasion because of Mr Blair’s informal “sofa-style” approach to government.

Last week, Tory backbencher Sir David Amess told MPs he would put down a measure in the Commons to impeach the former PM should the inquiry find him "guilty of misleading the House" about the threat to Britain posed by Saddam Hussein’s regime ahead of the 2003 invasion.

Alex Salmond, who with other MPs failed to impeach Mr Blair in 2004, has already made clear he too will seek to impeach the former premier if the inquiry concluded he misled the UK Parliament.