Boris Johnson’s first policy announcement, a pledge to ban alcohol on public transport, came under fierce criticism from unions yesterday and suffered a further setback when it emerged that the measure could not be implemented across the network.

The new Mayor of London said that the plan would improve safety and security on public transport in the capital, but concerns were raised that it would be almost impossible to enforce.

From June 1, passengers will be ordered off Tube trains and buses if they consume alcohol while on board. However, staff working for Transport for London and British Transport Police will not have the power to fine passengers, and officials admitted that there would not be regular patrols of carriages.

Instead, Mr Johnson will rely on a “cultural shift” and self-policing to bring a halt to drinking in the same way that passengers help to enforce the Tube’s no-smoking rules. He said that there would be a “rapid rollout” of another election promise, an extra 440 police community support officers, to help to enforce the plan. “Too many people have the unpleasant experience of sitting opposite someone swigging a can of lager,” Mr Johnson said. The ban will be brought into force by changing the conditions of carriage on London transport, but until it is enshrined in a bylaw, which the mayor said would take about a year, there is no punishment available to transport staff except for ejection.

Transport for London said that the measures applied to all public transport in the capital except on trains serving the national rail network. Peter Hendy, the Transport Commissioner, said that discussions had begun with the Department for Transport in the hope that the national rail network’s bylaws would be reviewed. However, a spokesperson for the department toldThe Times:“We have no plans to introduce these measures on the national network. Train companies already have powers to deal with any antisocial drinking on trains.”

The measure also drew criticism from transport unions, which said that it had not been thought through and that it could endanger staff who approached drunken passengers. Bob Crow, the RMT general secretary, said: “Violence against our members is already a major problem, particularly from people who have been drinking.

“Perhaps the mayor will come out with his underpants on over his trousers like Superman one Saturday to show us how it should be done, and maybe tell a crowd of Liverpool supporters that they can’t drink on the train.”

Tube workers told The Times that while the plan had merit, it would be difficult to enforce. One worker said: “It is a great idea if there was a chance you could carry it out, but I think it will be very difficult. How are we supposed to do it? We can’t search every bag.”

The mayor continued to reshape the Greater London Authority administration yesterday and appointed Brian Coleman, a Conservative member of the London Assembly, to chair the Fire and Emergency Planning Authority.

In a signal that a rivalry between Mr Johnson and David Cameron could be warming up, the Conservative leader warned the mayor that if he had his eye on Westminster after City Hall, he would have to wait his turn. He told The Spectator: “I am a big Boris fan. I have known him for a long time. I have always said to people: do not underestimate the brains and ambition of this guy. So when I’ve had a go, I’m sure there will be a queue of people looking to take over.”

While Mr Johnson’s tenure in London will be seen as a test run for the Conservatives, Mr Cameron said: “All Conservative councils and mayors are part of what people should expect from the Conservative party. But Boris is his own man, he is his own mayor and we are not going to agree on everything.”

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