Downing Street has said it played no part in the ousting of a top intelligence official who criticised Tony Blair's Iraqi arms claims.
Morrison said there was disbelief at Blair's claims on Iraq
John Morrison said Whitehall gave a "collective raspberry" to the prime minister's claim Saddam Hussein posed a "serious and current threat" to the UK.
His contract as chief investigator to the Intelligence and Security Committee is not being renewed.
The prime minister's spokesman said it was a matter for the committee.
Mr Morrison has worked for the committee for the last five years. His contract expires in October.
Mr Morrison's comment that intelligence officials reacted in disbelief to Tony Blair's claim came in a BBC Panorama programme broadcast two weeks ago.
"When I heard him using those words I could almost hear the collective raspberry going up around Whitehall," he told the programme.
"The prime minister was going way beyond anything any professional analyst would have agreed."
On Monday the Cabinet Office confirmed Mr Morrison would not be staying on.
He has reportedly been sacked and is working out his notice.
"Mr Morrison has worked for the committee for five years and his contract will end in October 2004. The committee has no plans to employ a new investigator," a spokeswoman said.
Former chief of Defence Intelligence and former deputy chairman of the Joint Intelligence Committee, Air Marshall Sir John Walker, worked with Mr Morrison,
He told the Today programme his going was a "very serious" development.
"John Morrison was an extremely experienced, extremely good intelligence operative. I had the highest regard and respect for him," he said.
"He has broken ranks, together with people like Dr Brian Jones and David Kelly, because of a considerable concern about what was going on.
Dr Brian Jones, formerly of the Defence Intelligence Staff told Panorama no-one on his staff had seen evidence of the scale of weapons capability being touted by Downing Street.
Sir John added: "If people of John Morrison's calibre break rank, it's very serious.
"These are people who for a lifetime have been loyal honest hardworking servants of the state, well used to not breaking rank, and now they have.
He said it was "beyond belief" Mr Morrison was going because his contract was up and he would be surprised if pressure had not come from Number 10 after the "embarrassment" of the Panorama criticisms.