Dr Jones questioned Tony Blair's evidence to the Hutton Inquiry

This comes as the government prepares for the Butler report into how intelligence on Iraq was handled.

Dr Brian Jones, a retired top Defence Intelligence Staff (DIS) official, told BBC's Panorama he was "confused" by Mr Blair's evidence in the Hutton Inquiry.

John Morrison, former deputy chief of DIS, said Mr Blair's claims on Iraqi WMD were met by disbelief in Whitehall.

'Unreliable'

Their statements appear to challenge assertions by the prime minister in the run-up to war that Iraq posed a "current and serious" threat to Britain.

Spy chiefs have gone as far as retracting intelligence behind Mr Blair's pre-war claims.

The prime minister was going way beyond anything any professional analyst would have agreed John Morrison Former deputy chief of DIS What will Butler say?

An anonymous senior intelligence source told Panorama MI6 had withdrawn the assessment underpinning Mr Blair's case.

Meanwhile Dr Jones told Panorama he "couldn't relate" to the prime minister's evidence to Lord Hutton on Iraq's weapons of mass destruction.

Mr Blair told the inquiry there was "a tremendous amount of information and evidence coming across my desk as to the WMD and programmes associated with it that Saddam had".

But Dr Jones, a critic of the government's Iraq dossier, told Panorama: "Certainly no-one on my staff had any visibility of large quantities of intelligence of that sort."

He said no-one knew what chemical or biological agents had been produced since the first Gulf War and there was no certainty among intelligence staff that agents had been stockpiled.

"There was a reasonable assumption that there may have been some stocks left over from the first Gulf War," Dr Jones said.

"If there had been any other production, then we have not identified that it had taken place."

Dr Jones told the Hutton Inquiry the dossier on Iraq was misleading because advice from DIS experts had been over-ruled by the Joint Intelligence Committee (JIC) which drafted it.

'Collective raspberry'

Mr Morrison told Panorama he could "almost hear the collective raspberry going up around Whitehall" when the prime minister told MPs the threat from Iraq was "current and serious".

He accused Mr Blair of making public statements which went beyond what experts could have reasonably concluded from the same evidence.

Liberal Democrat leader Charles Kennedy said people wanted "straight answers to straight questions over the war."

Speaking ahead of two key parliamentary elections this week, Mr Kennedy added: "Now this government are just losing the plot.

"They are turning in on themselves and they are turning their back on the voters.

Lord Butler's findings are due to be published on Wednesday evening

"In moving from what the dossier said Saddam had, which was a capability possibly, to asserting that Iraq presented a threat, then the prime minister was going way beyond anything any professional analyst would have agreed," he said.

Mr Morrison said analysts came under pressure after Operation Desert Fox, the bombing campaign against Iraq in 1998.

Analysts had felt pressured to back claims targets actively involved in WMD production had been hit in the strikes - even if they were not sure that was the case.

Panorama also claimed John Scarlett, chairman of the JIC, was warned a month after the dossier's publication the intelligence was not strong enough to back the presentation of some of its claims.

Mr Scarlett may be among the intelligence bosses singled out for criticism in Wednesday's report.

But the Sunday Times reports Mr Blair will stand by Mr Scarlett even if the new head of MI6 is criticised.

Meanwhile the Sunday Telegraph reports the prime minister's chief of staff Jonathan Powell is likely to be come in for criticism.

Panorama: A failure of intelligence will be broadcast on BBC One at 2215 BST on Sunday.