Derek Simpson, the new general secretary of Amicus, the engineering and electricians’ union, claims that allies of his predecessor could be behind allegations that he enjoys lavish perks despite his promise to be a “no frills” leader.

Westminster was awash last week with talk of Simpson having the use of a fleet of cars and three secretaries, undertaking an extravagant refurbishment of his offices and staying in luxury hotels at the union’s expense.

Simpson claims that supporters of Sir Ken Jackson, the Blairite former leader of the union whom he unexpectedly beat to get the job last summer, might have inspired the campaign.

He said that the other possibility was that “disgruntled former employees” of the union were making the claims about him.

The rivalry between the two camps has caused bitter infighting that has been fuelled by Simpson announcing an inquiry into alleged misuse of union funds and vote-rigging during Jackson’s leadership.

Claims about Simpson that have been circulating within the last few weeks include: oAn allegation that he has the personal use of two Vauxhall cars and a Ford people carrier. He says that while it is true he has the use of a Vauxhall Vectra and an Omega estate, he has merely had lifts in the people carrier, which is allocated to Sir Roger Lyons, the joint general secretary. o That he insists on upgrading to a better hotel when he stays in London. Simpson admits he has switched from the Holiday Inn in King’s Cross to a Radisson Edwardian, but claims the union gets a discount rate and the facilities are more suitable. o That he has three secretaries and even his personal assistant has a PA. He claims he alone has a PA and shares the use of a pool secretary. o That he has ordered a lavish refurbishment of the union’s offices in Covent Garden and in Bromley, south London. Simpson claims he has merely repainted his office in Bromley and that the central London offices were due for a refit anyway. o That he has advertised for a chauffeur to drive him around even though he promised not to use one as Jackson had done. He admits the union has advertised in the press for a chauffeur, but says it will be for the use of all officials and that he regularly uses the train and Tube to get to meetings.

“People are seeking to undermine me and have me removed,” said Simpson last week.

“It is clearly someone who has got a grouse. I suppose on the face of it, it all looks like good copy, but the reality is that it is not true.

“The union is a £100m business and I have a PA and a temporary secretary who doesn’t actually work for me.

I think most people think my regime is better.”

The bitter rivalry began when Simpson, then a relatively unknown regional official at the union, unexpectedly beat Jackson in last July’s leadership ballot.

Jackson’s supporters were so confident that their man would win, they even baked him a cake inscribed with the words “Ken Jackson is a winner” and arranged a victory party. Although he initially scraped home by just 807 votes, a series of recounts gave Simpson victory by a narrow 300 votes.

Simpson promised to be more independent of the Labour leadership and cut funding, while Jackson approved a £2m donation to the party at the last election and followed the official line.

Simpson, a former communist, has promised to be a different kind of leader to Jackson, who was often dubbed “Tony Blair’s favourite union leader”. Simpson told The Sunday Times last year that he planned to give the prime minister a “f****** migraine” in the battle for better workers’ rights. His threat comes amid increasing militancy among trade union leaders.