Ken Livingstone said he would not apologise for "telling the truth" after he was suspended from the Labour Party for a further year over the controversial remarks he made about Adolf Hitler and Zionism.
The former London mayor, who had threatened to launch a judicial review if he was expelled, said he would now consult with lawyers about his legal position.
The veteran left-winger earlier said he had expected to be expelled because the disciplinary panel investigating the case was dominated by “right-wingers”.
A hearing into Mr Livingstone's conduct had resumed on Tuesday afternoon, where party bosses decided his fate following his controversial claim that the Nazi leader supported the creation of a Jewish state.
Mr Livingstone - who has been suspended since April last year - faced a charge that he engaged in conduct which was "grossly detrimental" to the party.
It followed a radio interview in which he claimed that Hitler had supported Zionism in the 1930s before he "went mad and ended up killing six million Jews".
Speaking after the hearing concluded in the evening, he told reporters he would not retract his remarks or apologise "for telling the truth”.
Mr Livingstone said: "I expected them to expel me, so I've now got to consider whether I challenge this legally or just live with it."
He said the experience "was like sitting through a court in North Korea".
He maintained that he had not brought the party into disrepute, saying: "There's an issue here that matters - should someone be disciplined for stating a historical truth, and I think that's really important.
"Labour MPs who tweeted that I was anti-Semitic, that I had said that Hitler was a Zionist, I was a Nazi apologist, no disciplinary action against them.
"I think that's a double standard that's unacceptable. MPs can't be treated differently to ordinary party members. You can't apologise for telling the truth."
The ex-mayor later said he would launch a campaign to have the suspension overturned.
"The Labour Party's disciplinary process was not in accord with natural justice in a number of ways. For example the panel hearing was not held in public, despite the fact that it could have been under Labour's rules. I was suspended for more than 11 months before the hearing was held," he said.
"I will be launching a campaign to overturn my suspension of party membership."
He insisted that he had never said Hitler was a Zionist, only that Hitler had supported Zionism at one time.
His case was decided by Labour's national constitution committee, which heard two days of evidence behind closed doors before adjourning on Friday.
A Labour Party spokesman said: "The National Constitutional Committee of the Labour Party has today found that all three charges of a breach of the Labour Party's rule 2.1.8 by Ken Livingstone have been found proved.
"The NCC consequently determined that the sanction for the breach of Labour Party rules will be suspension from holding office and representation within the Labour Party for two years.
"Taking account of the period of administrative suspension already served the period of suspension will end on 27 April 2018.
"The Labour Party will make no further comment on this matter."