A 24-hour strike on London's underground rail network will go ahead on Monday after talks over planned job cuts broke down, heralding the fourth walk-out since September.
The strike, by members of the RMT and TSSA unions, will begin on Sunday evening, and is likely to cause further travel disruption for thousands of commuters already facing treacherous weather conditions.
"If they are serious about resolving this issue, they should call off their totally unnecessary strike immediately," London Underground's (LU) chief operating officer Howard Collins said in a statement.
Transport for London (TfL), which runs the network, said its offer of a further six weeks of talks to review staffing plans and safety concerns, was turned down by the unions. Talks have been going on for six months.
But RMT said LU had rejected its proposal to suspend action for 12 weeks in return for a 12-week halt to the cuts for the safety review.
"This strike is about safety and we will be taking that message to passengers as we build the campaign against the tube cuts," RMT general secretary Bob Crow said in a statement.
TfL said more than half the 800 proposed job reductions had been achieved through voluntary redundancy and not filling vacant posts, and would not impact safety.
The planned changes, earmarked for next February, are driven by falling ticket office sales, it said.
The network carries some 3 million passengers daily and business lobbies have said the stoppages cost the capital up to £50 million per day.