By politics.co.uk staff
A high court challenge and disputes over its impact loomed as a 48-hour strike by London Underground maintenance staff approached.
Around 1,000 Rail Maritime and Transport union staff are set to walk out for two days from 19:00 this evening in a dispute over pay and conditions.
Transport for London said the industrial action would not affect the London Underground's service.
"Should the action go ahead, we do not anticipate any significant impact to Tube services and London Underground intends to operate a full service on all lines," a spokesperson said.
But union leaders predicted significant disruption as emergency response and intersection workers would also participate.
Tube Lines, the private firm responsible for upgrading the Northern, Jubilee and Piccadilly Lines, issued a statement on its website stating a three-year deal had been rejected by the RMT.
It is launching a high court bid to get the strike quashed, following a series of higher-profile industrial disputes which have seen industrial actions prevented from taking place.
RMT general secretary was quoted by the Guardian as saying the strike would have a "major impact".
He expressed the hope that London mayor Boris Johnson, who takes over control of Tube Lines next week, would intervene to resolve the dispute.