The Scottish National Party has suspended rebel MSP Campbell Martin from the party for six months.
Campbell Martin attended a disciplinary hearing
Mr Martin, who has been sharply critical of John Swinney's leadership, was accused of acting against the interests of the party.
He has repeatedly called for Mr Swinney to be replaced as party leader.
After a two-hour disciplinary hearing, Mr Martin said he was disappointed. He added that he would continue to fight for what he believed in.
The MSP had already been suspended from duty before appearing before the party's national executive at a disciplinary hearing in Edinburgh on Saturday.
The party's executive had the options of extending his suspension, expelling him, rebuking him or dismissing the complaint altogether.
Mr Martin, 44, was suspended from the party on 25 April after making repeated public criticism of John Swinney's leadership.
He was accused of conduct "inimical to the interests of the party".
His case went before the SNP's 32-member national executive committee at the party's headquarters, who voted 24 to 4 to suspend him.
Speaking after the hearing, Mr Martin denounced the decision as "flawed" and insisted he would go on speaking his mind.
He said: "They can suspend me from the party but they can't suspend me from thinking, or from speaking."
A statement from the SNP confirmed the decision and said Mr Martin had 21 days to appeal.
Nationalist leader John Swinney said the suspension was because Mr Martin had undermined the party by threatening to quit.
He said: "The party is not going to tolerate individuals who will damage the direction of the party.
"We're quite open for democratic debate, for criticism, for open discussion about how the party should proceed.
"But we draw a line when people try to damage the party and our executive has come to what I consider to be a sensible and a measured decision."
Mr Martin learned of his initial suspension when Mr Swinney announced it during a radio interview after the SNP's spring conference.
The West of Scotland regional MSP had said in a magazine interview last month it was "beyond question" that the SNP needed a new leader.
He has insisted he was speaking for a "sizeable body of opinion in the party" which backed a stronger line on independence but had been ignored by Mr Swinney.
Mr Martin now plans to consider his next move, but said he did not intend to
stand down as an MSP.
Critics of the MSP say he has persistently undermined the leader - and consequently the SNP.
However, his supporters argued he only said openly what others thought - and that criticising the leader was not enough to warrant expulsion from the party.