The writer and former minister for posts and telegraphs, Dr Conor Cruise O'Brien, has said he resigned from the UK Unionist Party because his analysis of the North had put the leader, Mr Robert McCartney, in a "very difficult position".
In an interview published in The Irish Times today, he denied Mr McCartney had forced him to quit. "He didn't ask me to resign or want me to resign, but he saw eventually that I would have to. I proposed it and he finally agreed to it."
The move followed publication of extracts from Dr O'Brien's forthcoming book of memoirs in two Sunday newspapers. He forecast that the growing influence of Sinn Fein and the Provisional IRA in Northern life would force unionists to consider entering a united Ireland with constitutional nationalists.
In a letter to Mr McCartney yesterday, he said he was resigning "with deep regret" but that it was required "both in the interests of the party and of my own freedom as a writer".
He added: "Since the analysis or hypothesis in my memoirs adumbrates the view that in certain future circumstances the preferred outcome might be a negotiated united Ireland, I appreciate that even though this is merely opinion it has occasioned opportunities for the distortion of the party's policy in the media."
He acknowledged that many members of the party seemed to be "genuinely dismayed" by the excerpts published on Sunday. If he remained in the UKUP, the articles would be exploited by the party's enemies.
Dr O'Brien's articles had become a weapon in the conflict between the different unionist parties. At Stormont on Monday, a member of the UUP held up a copy behind Mr McCartney's back while the UKUP leader was addressing the Assembly.
Mr Reg Empey of the UUP said yesterday: "It is now obvious that Mr McCartney has brought a cuckoo into the unionist nest. It is perfectly clear by Dr O'Brien's remarks that the UKUP has a defeatist attitude to maintaining the Union."
For his part, Mr McCartney attacked "political pygmies" in the UUP who, he claimed, had prompted Dr O'Brien to quit. He said he not only admired Dr O'Brien but loved him.
Dr O'Brien, a man of international standing, was a true friend of the Union, but the UUP had exploited his "analysis or hypothesis". It was an "absurd nonsense" for anyone to suggest that the UKUP could even continue as a party were it to negotiate a united Ireland, Mr McCartney said.
Mr Ruairi O Bradaigh, the Republican Sinn Fein leader, joined in the controversy by saying that Dr O'Brien's analysis was in keeping with the one he had been proposing since 1969.