Whitehall union in turmoil as officials row over leadership

One of Britain's biggest and most anarchic trade unions was in turmoil last night after two men claimed to be the rightful leader.

Once renowned as the "Beirut of the trade union movement", the Public and Commercial Services Union, which negotiates with ministers on behalf of 270,000 Whitehall staff, erupted into another bout of fratricide.

Amid scenes of near-riot at the union's London headquarters, a newly constituted national executive with a "moderate" majority voted by 25 to one to strip the hard left general secretary-elect, Mark Serwotka, of his post.

As rival factions traded insults, the meeting decided to declare Mr Serwotka's election unconstitutional and call on the right-winger Barry Reamsbottom, who enjoys the support of the Prime Minister, to carry on as general secretary beyond his supposed retirement date of 31 May.

Mr Reamsbottom, a supporter of New Labour, had been advised that the process by which his rival had reached his position was unlawful and the executive, dominated by his supporters, agreed. Left-wingers, however, accused him of orchestrating a "coup d'êtat".

Mr Serwotka won an election to become general secretary in 2000 on an anti-privatisation platform, beating his moderate rival Hugh Lanning by 41,000 to 33,000 votes.

Mr Reamsbottom, 53, who did not stand in the poll, said the former left-dominated executive had "manipulated a vacancy where none existed".

He insisted he had never agreed to retire at the end of the month and accused Mr Serwotka's supporters of "outrageous" behaviour at yesterday's meeting – an allegation reciprocated in full measure.

"I've fought Trots all my life, but I've never witnessed scenes like it in all my years in the union movement," he said.

Mr Serwotka said the disturbances were caused by his opponents. He described the attempt by Mr Reamsbottom to remain in the job for another two years as "an absolute outrage and an affront to democracy" and a negation of a legal agreement he had signed.

He pointed out that Mr Reamsbottom did not stand in the election because he did not receive enough nominations and had not challenged the result until yesterday. He also said the union's annual conference last week had confirmed the result by 1200 votes to about 20.

* Staff at the British Museum are threatening strike action in protest at plans to axe 150 of its 1,100 employees. They fear the cutbacks, which were announced after the museum said it faced a deficit of up to £6.5m, will cause irreparable damage to its invaluable collections.