Ken Livingstone, the Mayor of London, has claimed he is the victim of a “hatchet job” by Channel 4 after a series of accusations about his running of City Hall.

A Dispatches documentary to be broadcast tonight is expected to claim that many of his senior advisers were members of a Trotskyite faction which plotted to turn the capital into a “socialist city state”.

The programme makers also reportedly tested the mayor’s drink at a public meeting and will allege that it contained whisky. The programme, made by Martin Bright, the political editor of the New Statesman, will claim that his drinking habits have attracted criticism from fellow politicians.

Last night a spokesman for the mayor released a statement denouncing the programme’s claims as “ludicrous” and accused it of smearing Mr Livingstone.

The mayoral election, on May 1, is expected to be the tightest he has faced since he first ran for the post in 2000.

One of the interviewees for tonight’s programme is expected to be the mayor’s former senior adviser on Asian issues, Atma Singh. Mr Singh said at the weekend that many of the mayor’s senior advisers were members of a Trotskyite faction called Socialist Action which plotted to turn London into a “socialist city state”.

Mr Singh said: “Socialist Action decided to operate as an ‘entryist’ organisation. Ken Livingstone wanted political power. Socialist Action organised his campaigns successfully and dealt with spin. Livingstone was never a member of SA but he was close to the group — almost like the leader.”

Mr Livingstone’s spokesman said last night that Mr Singh was an “embittered ex-employee” who had been removed from his post.

The statement claimed that Dispatches had been “totally discredited” by its controversial documentaries on Aids and climate change, adding: “It has been pointed out to Channel 4that the allegations against Ken Livingstone, in the hatchet job on him by journalist Martin Bright for Dispatches, are equally ludicrous.”

On Saturday there were calls for an inquiry into claims that the mayor’s office ran a campaign using public money to undermine the equality chief Trevor Phillips. The BBC Radio 4 Today programme said it had obtained e-mails showing that the mayor’s equality adviser, Lee Jasper, orchestrated a campaign to prevent Mr Phillips from becoming chairman of the Commission for Equality and Human Rights. The Greater London Authority denied that Mr Phillips had been undermined.

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