Lord Owen was in favour of the war

The former Labour foreign secretary said it could be decades before the joint intelligence committee (JIC) recovered from the damage it had suffered.

Lord Owen argued that British intelligence agencies had been turned into a "laughing stock" by the government's dodgy dossier, which was later found to be based on a PhD thesis posted on the internet.

And the SDP founder criticised JIC chairman John Scarlett for allowing Tony Blair's communications chief, Alastair Campbell and Number 10 chief of staff Jonathan Powell to make changes to the earlier September dossier.

Speaking ahead of the results of the judicial inquiry into the death of government weapons expert Dr David Kelly being conducted by Lord Hutton, he said that although he did not feel duped over the way the case for war was presented, millions did feel "deceived".

Speaking at the London School of Economics, Lord Owen said: "I do not need to await Lord Hutton's verdict to judge that the joint intelligence committee machinery, which I have known well and respected, was corrupted in the run up to that war in a way which will leave damage for decades to come.

'Shambolic'

"It is impossible to believe that Sir Anthony Duff, Sir Percy Craddock or Dame Pauline Neville-Jones, to name but three heads of the JIC with whom I have worked, would ever have conducted themselves as John Scarlett did with Jonathan Powell and Alastair Campbell over amending the statement on Iraqi weapons of mass destruction.

"The other so-called 'dodgy' dossier on which Alastair Campbell has already apologised left our joint intelligence services a laughing stock.

"Amongst the reasons for these failures is the 'matey', corner-cutting, somewhat shambolic structure of No 10's defence and security decision-making which were revealed in the Hutton hearings."

Mr Scarlett, Tony Blair, Alastair Campbell and other Downing Street officials all told Lord Hutton the dossier was put together and approved by the Joint Intelligence Committee, with no interference from Downing Street, other than presentational advice.

Lord Owen, who supported the war, also attacked the absence of effective planning to cope with post-war Iraq.

In particular he criticised the failure of the US-led coalition to anticipate a guerrilla-style campaign against occupying forces.

And he urged a full-scale inquiry into the war similar to the Franks inquiry into Falklands conflict.