The DUP leader, Ian Paisley, has said the Ulster Unionist leader, David Trimble, should quit while the going is good.
After Mr Trimble's declaration yesterday that he did not intend to resign his post, Mr Paisley said if the Upper Bann MP had any sense, he would step down following recent defections from his party.
Mr Paisley was speaking to reporters in Belfast after a meeting with PSNI Chief Constable Hugh Orde.
Last week, rebel MP Jeffrey Donaldson and MLAs Arlene Foster and Norah Beare quit the Ulster Unionists, saying they no longer had confidence in the party and believed that it no longer represented their values.
Mr Donaldson revealed he had been invited to join Mr Paisley's negotiating team in the New Year review of the Good Friday Agreement, and would make a final decision on whether he would join the DUP after the Christmas holiday.
After a meeting of party officers yesterday to discuss the resignation, MrTrimble said he was planning to submit his name for re-election as leader in March at the annual general meeting of the Ulster Unionist Council.