Former SNP minister Fergus Ewing has been suspended from the party for a week after a disciplinary vote by MSPs.
Mr Ewing has been a critic of the party leadership and had voted against the government in a no-confidence motion.
The SNP's Holyrood Group confirmed the proposal was backed by 48 votes to nine with four abstentions.
In a statement after the vote, Mr Ewing said he was "literally born into the SNP".
He added: "The SNP I joined would never have asked me, or indeed any other elected politician, to choose between loyalty to party and loyalty to constituents.
"Indeed in the old SNP it was always expected that country and constituency would come first.
"That is why the SNP, while often attacked, was always respected."
'Doing the right thing'
The veteran politician said he had always been loyal to the party as he felt it was attempting to "do the right thing by my constituents and for Scotland".
He continued: "It was never an ordinary political party because it was one which put Scotland first.
"In good conscience this is no longer the case and it has nothing to do with personalities or my antipathy towards the Green Party."
After listing several policies he disagreed with Mr Ewing's statement reflected on the dilemma he now faced.
It concluded: "I choose to defend my constituents and Iet the cards fall as they will."
Mr Ewing has been an MSP since the Scottish Parliament was created in 1999 and is the son of SNP icon Winnie Ewing, who died in June aged 93.
Mr Ewing was represented at the hearing by lawyer John Campbell KC. He has two weeks in which to appeal the decision before the punishment begins.
First Minister Humza Yousaf returned home due to illness before the vote and did not take part.
Former first minister Nicola Sturgeon was also not present as she was hosting an event elsewhere in parliament, according to the BBC.