A transport union is set to unleash travel chaos on London on the eve of the city's May 1 mayoral elections with a two-day strike on the Underground train network.
Some 2,500 workers are to stage a 48-hour strike from April 28, the National Union of Rail, Maritime and Transport Workers (RMT) said, in a spat linked to the collapse of maintenance firm Metronet.
The planned industrial action would likely cripple Underground services in the British capital and come as the campaigns for the London Assembly and mayoral elections hit their peak.
Maintenance staff voted by four to one for strike action.
"Despite weeks of detailed talks and positive discussions with the mayor, we have still not won an unequivocal, written guarantee we are seeking to protect our members' interests," said RMT general secretary Bob Crow.
The strike was called after the union said it failed to receive written guarantees on outsourcing, pensions and travel facilities of 2,500 workers formerly employed by Metronet.
The RMT's three-day strike in September nearly paralysed the network and left millions of commuters facing a gruelling ordeal simply to get to work.
In the mayoral vote, incumbent Ken Livingstone, from the Labour Party, is facing a strong challenge from Conservative candidate Boris Johnson, with polls either putting Johnson ahead or the pair neck and neck.
London's burdened transport network has been one of the main battlegrounds in the campaign. (AFP)
London faces Tube strike ahead of mayoral vote