Ulster Unionist leader mr David Trimble has accused dissidents in the party of wanting to go back to "Stone Age politics".
This weekend the party's 900-strong ruling council meets to debate a motion condemning Mr Trimble's attempts to take disciplinary action against three MPs who quit the parliamentary whip in protest at his peace process policies.
Mr Trimble said the MPs - party president the Rev Martin Smyth, Mr Jeffrey Donaldson and Mr David Burnside - had gone over the top when they quit in June and should stop trying to split the party.
In a thinly-veiled attack on the three men he said he knew there were people in the party who had genuine concerns about the peace process, but there were some who "seem to be searching for any excuse to try to derail the political process and say no, and go back to Stone Age politics".
However he said they were "a very small minority".
He said the three MPs had escalated the internal party disputes in June in what was an attack not just on party policy but on the party leadership and the party structure.
In a hard-hitting attack he said: "That was ever so slightly over the top and I hope that they will reconsider this and not split the party as they are threatening to do."
He insisted his personal position as leader would be unaffected by the vote on Saturday - win or lose - it was about the position of the three MPs.
"I hope they will regularise their position," he said urging them to "be loyal to the party and to behave responsibly".
Mr Trimble said if the issues they were concerned about were issues of policy, if there were genuine concerns about things, they could be dealt with.
He was prepared to make another effort to bring people back into the party mainstream, he said, adding: "But when you have an all-out assault on the integrity of the party you have a slight problem."
Mr Donaldson, Mr Burnside and Mr Smyth angered supporters of Mr Trimble in June by resigning the whip at Westminster in a dispute over party policy.
PA