The leader of Ulster Unionist Party, Tom Elliott, said he has no regrets in disciplining senior colleague David McNarry, claiming the MLA's decision to resign from the Assembly group in protest was an over-reaction.
Mr McNarry dramatically quit on Friday night after Mr Elliott demoted him from a Stormont committee position for remarks he made in a media interview about UUP talks with the DUP.
The Strangford MLA took his seat alongside independent members in the Stormont chamber today, claiming he had been overwhelmed with messages of support following his decision to walk away from the Assembly group.
As the fall-out from the affair continued, his party leader stood by his call to remove him as vice-chairman of the Education Committee.
Mr Elliott acknowledged that he was aware Mr McNarry was going to give the interview to the Belfast Telegraph about the discussions with the DUP, but claimed his colleague had not stuck to agreed party lines and had overstated the potential link-up with their unionist rivals.
He said Mr McNarry's claim that in the future the DUP could hold Stormont's first minister position, with the UUP holding the office's junior minister post had particularly angered him.
"We have a vast number of members in the Ulster Unionist Party and the vast majority of them are very well-disciplined members but I have been under pressure for a couple of years now to ensure that there was discipline within the party and I believe that David went beyond his remit in his interview with the Belfast Telegraph," he said.
"Not because he was talking to the DUP, that was not an issue, because he was mandated to do that, but the issue was around how far he went in the interview.
"He had informed me that he was going to carry out the interview and that I had said 'that's fine, providing you stick to the course and lines we have issued', but I believe he went far and beyond that.
"It wasn't a hanging offence, the punishment certainly wasn't severe, all I was doing was to remove the vice-chairmanship of the Education Committee.
"Lots of people in this party don't have any chairman or vice chairmanships so I just believe it was the least level of punishment you could offer at all. But he decided to remove himself, or he had said he is removing himself, from the Assembly group.
"I had hoped he wouldn't have done that, that certainly wasn't my intention.
"I have known David for a long, long time, so it disappoints me."
Mr McNarry contacted Speaker William Hay's office in the afternoon to resign officially from the UUP Assembly group.
An Assembly spokeswoman said: "The Speaker has received a letter from David McNarry, MLA, advising that with effect from 30 January 2012 he wishes to be regarded as an independent member of the Northern Ireland Assembly whilst retaining his designation as a 'unionist'."
But Mr McNarry has insisted he has no intention of quitting the wider Ulster Unionist party.
Despite overtures from the DUP to join its ranks, Mr McNarry made clear he would not be voluntarily leaving the party he joined as a 15-year-old.
"I have no intention of quitting the party," he vowed.
Mr McNarry's comments to the media prompted Mr Elliott to write a letter to party members playing down the significance of the discussions with the DUP.
Today the Strangford member claimed that he had got a lot of support in the wake of his decision to leave the Assembly group.
"I have been overwhelmed by the support I have received since Friday," he said.
"I have had over 140 emails, texts and phonecalls. Some from colleagues but most from people I don't even know.
"That tells me something about what has happened."
But Mr Elliott said his colleague could have responded to the punishment in a better way.
"I said to David I thought we could have dealt with this in a more positive and practical matter and resolved it," he said.
"It's like a lot of things: take what's coming and get on with life. Unfortunately I believe he over-reacted."
The party leader said UUP members had overwhelmingly backed his stance.
"I have to say almost all the people who have spoken to me have said we had to have discipline somewhere, we are pleased to see that someone has started."