The ex-US diplomat at the heart of the political crisis in the White House says Tony Blair was "double-crossed" on the reasons for going to war with Iraq.
Mr Wilson disputes that Iraq was acquiring nuclear weapon material
Joseph Wilson said he believed the Mr Blair had thought he was getting involved with a "disarmament campaign".
But "he was double-crossed by the regime change crowd in Washington" and ultimately had "no choice" but to go along with a regime change war.
Mr Wilson told BBC Radio 4 the White House had "hyped the nuclear case".
Mr Wilson was acting ambassador to Iraq in the run-up to the first Gulf War. In 2003 he was the envoy sent to Africa to investigate reports that Saddam Hussein had tried to buy nuclear material there.
He told the Today programme: "Mr Blair came to the US when Mr Bush was talking about regime change, and when he left Mr Bush started talking about disarmament as the objective.
"Mr Bush went to the United Nations, I think that that had a lot to do with the influence of the British.
"I think that Mr Blair really thought that he was getting involved in a disarmament campaign, which was all to the good - I fully supported that.
"I think at the end of the day he was doubled-crossed by the regime change crowd in Washington."
This meant that when the weapons evidence was then questioned at the UN, Tony Blair was put into a position where he then "had no choice" but to go along with the war anyway, said Mr Wilson.
He argued the Bush administration had used the nuclear threat to gain Senate and public opinion.
Mr Wilson's wife Valerie Plame was allegedly "outed" as an undercover CIA agent by senior administration figures in retaliation for his report before the war which concluded that Saddam Hussein had not bought uranium in Niger.
Vice-president Dick Cheney's chief of staff, Lewis Libby, is facing charges including perjury and obstruction of justice after investigtions into claims he disclosed to the media Ms Plame's role as a CIA operative.
Mr Wilson said on Thursday: "It is very clear that some of the evidence relating to the justification for the war was twisted. There was never any substance to the allegation that Iraq had attempted to purchase quantities of uranium from Niger.
"Even after it had been discounted both to the Senate and to the White House, the president used it in his State of the Union address (in January 2003)."
Mr Wilson said that four months before that State of the Union speech, the CIA's deputy director warned the Senate that it believed that British intelligence sources - which had supplied the Niger uranium allegation - had "stretched the case".
He continued: "I believe that the president and this administration had come to a decision that it wanted to go to war with Iraq.
"It had seen the Use of Force Authorisation Bill, which required that it demonstrate to itself that the threat was serious, and that the only way that they were going to be able to get both Congressional support and American public support was by hyping the nuclear case."
The White House has always denied that Mr Wilson' wife was revealed as a CIA agent in retaliation for the former ambassador's report scotching the administration's claims about Iraq's nuclear ambitions.
Downing Street continues to say it was right to go to war because Iraq had flouted United Nations weapons rules.