They have not spoken for years. Yet tonight London Mayor Boris Johnson accused RMT boss Bob Crow of “holding a gun” to the capital’s head as both sides failed to avert a London Underground strike.

Mr Crow, leader of the RMT union, and the London Mayor clashed ahead of tonight’s expected tube strike in a dispute over ticket office closures. The strike, over the next 48 hours, is expected to bring travel chaos for millions of people.

The RMT union, representing tube workers, and the Mayor of London say they are unwilling to negotiate until the other side blinks.

The row emerged over plans to close ticket offices and cut 750 posts in an attempt to save £50m a year.

Proposed redundancies

London Underground wants to move staff from ticket offices into ticket halls, and proposes redundancies.

However, Mr Crow said that having been presented with the redundancy plans before listening to his union’s arguments, he was not prepared to enter negotiations until the threat of job losses had been withdrawn.

Bob Crow said he was not prepared to enter negotiations until the threat of job losses had been withdrawn.

Mr Johnson accused Mr Crow of “holding a gun to Londoners’ heads” by staging the strike regardless.

Earlier, Mr Johnson said on LBC that he had not spoken to Mr Crow for “a few years”. Moments later, Mr Crow phoned in to the show, and had their first clash of the day.

‘Put guns away’

Mr Crow urged both sides to “put the guns away, put them in a cupboard, lock them up and have a mature debate”.

The RMT and the TSSA union oppose plans to close offices in favour of commercial outlets such as Amazon and Waitrose. The strike action comes after seven days of talks at the conciliation service Acas ended without agreement, and no plans were made for further negotiations.

Bob Crow’s tube strike is plain wrong and he should call it off today. David Cameron

The talks between Transport for London and the RMT and TSSA unions ended last night.

Mr Johnson described the strike action as “pointless”, saying that a thousand people had already applied for voluntary redundancy.

Today, David Cameron weighed into the row, saying: “Bob Crow’s tube strike is plain wrong and he should call it off today. His shameful plans will bring misery to millions of hardworking families in London.

“Ed Miliband should condemn the strike immediately – no ifs and no buts.”

Brazilian holiday

Mr Crow was also forced to defend a recent trip to Brazil, after photographs of him sunbathing appeared in newspapers over the weekend.

The RMT boss said he would have returned had he been needed and that he was in contact with negotiators.

About 10 million people a day are believed to use London Transport. London Underground recently commissioned a survey claiming that 82 per cent of people were in favour of the changes they propose.

Services are due to be affected from 9pm on Tuesday, with some services running only between the hours of 7am and 11pm on Wednesday and Thursday.

Some stations will be closed. Lines worst affected include the Piccadilly line, and the core route is to be prioritised on the District and Victoria lines.

The Northern line is expected to operate a near normal service.