Basil McCrea has lost the Ulster Unionist Party (UUP) whip over his stance on the Union flag dispute, the party leader has said.
He was accused by Mike Nesbitt of lacking self-discipline and the ability to work as a team following a dispute with his party over the flying of the flag at Stormont. The MLA will now not be bound by UUP rules at the Assembly.
Mr McCrea represents Lagan Valley and was defeated for the leadership of the party during an earlier election.
Mr Nesbitt said: "Basil's inability to exercise self-discipline or demonstrate the basic characteristics of teamwork are doing enormous damage to the Ulster Unionist Party.
"For the reasons of lack of self-discipline and teamwork, and for those reasons only, he has left me no choice but to remove the party whip with immediate effect."
On Monday he attended a UUP assembly group meeting which unanimously empowered the Assembly commission representative to discuss the issue of flying the flag at Parliament Buildings.
Within 48 hours he said it was not the right time to do what he had previously endorsed and later described Monday's decision as a "stupid idea".
The Alliance Party has led calls for the Stormont flags issue to be dropped until loyalist street protests over the decision to restrict the number of days the flag is flown from Belfast city hall end.