London Underground employees are to decide whether to strike over job cuts and Tube ticket office closures, transport union RMT announced yesterday.

Members of RMT will be balloted in the coming weeks on whether to launch a campaign of industrial action in the new year.

Voting will end in January and the union will have to give seven days notice of action if there is support for stoppages.

The announcement followed London Mayor Boris Johnson's unveiling of huge changes on the Tube, including a new 24-hour service at weekends and staff based in ticket halls and on platforms. All ticket offices would be closed.

There will be 750 job losses although London Underground (LU) said it would seek to avoid compulsory redundancies. The firm employs 18,000 people including 5,500 station staff.

RMT general secretary Bob Crow said: "It is absolutely clear that the attack on staffing levels and passenger services would have a devastating impact on Tube safety, with assaults and thefts soaring through the roof.

"The plans rip up promises on ticket offices that the mayor gave to London before he was elected."

The plans will deliver savings of around £50 million a year or £270 million over the term of Transport for London's business plan to 2020/21.

Mr Crow added: "RMT members have now had a chance to study in detail the proposals put forward last week by London Underground which would axe almost 1,000 staff jobs and close all ticket offices across the network.

"RMT has also now had a chance to thoroughly examine the risk assessment documents passed to the union by the Tube management."

Transport union TSSA is launching a campaign with the Labour Party to reverse the decision but has not announced a strike ballot.

The mayor said there would be a "proper period of consultation" with staff over the changes, adding that he hoped employees would see the benefit of the proposals. LU said only a small fraction of travellers use ticket offices.

Mr Johnson said: "I very much hope it will not come to a strike."