The RMT's Bob Crow: These issues aren't about extra money... this is about safety
Rail workers will take strike action on the four days after Easter in a dispute over jobs and working practices.
Talks between Network Rail (NR) and the RMT and TSSA unions at conciliation service Acas failed to reach agreement.
TSSA supervisors and RMT maintenance workers will walk out from 6-9 April, while RMT signal staff will strike from 0600-1000 and 1800-2200 on those days.
NR said a strike would have a "severe impact", and earlier predicted most services would be cancelled.
'Safer than ever'
RMT general secretary Bob Crow said: "RMT negotiators have worked flat out to try and reach an agreement that protects rail safety, job security and working agreements in the disputes involving signalling and maintenance staff on Britain's railways.
Nils Blythe, BBC business correspondent
Commuters will bear the brunt of the threatened rail strike. The signalling staff will walk out during the morning and evening rush hours on four days starting from 6 April.
Network Rail has contingency plans to keep some trains running during the strikes, but these are likely to be concentrated on the main routes between cities.
It is by no means certain that the strike will go ahead. The RMT and TSSA unions, as well as Network Rail, have been at pains to stress their willingness to resume talks.
And while there is no definite plan for further negotiations it is highly likely that discussions will resume before the first strike date.
Mr Doherty said the unions were willing to talk to try to resolve the dispute but that the two sides were still a long way apart.
The union leaders have made great play of avoiding upsetting the public with a strike over Easter. But passenger numbers over the Easter period are lower than at other times and the proposed strike dates after Easter will affect more people than a walkout over the holiday period.
"Despite long hours of talks, we have received nothing concrete from Network Rail that addresses the key issues."
TSSA general secretary Gerry Doherty said the strike was about "the safety of the travelling public and the safety and security of our members".
The unions said the rail network would be "effectively be closed down" by the industrial action, the first national rail strike since 1994.
There were fears that the strike would be called over Easter, but the unions said they deliberately avoided this in order not to disrupt the public over the bank holiday.
Robin Gisby, Network Rail's director of operations and customer services, disputed the unions' claims that the strike was about safety.
He said: "Britain's railway is safer than ever. The issue of safety is a smokescreen from a union leadership stuck in the steam age.
"Our contingency plans are well advanced and aim to keep as many trains running as possible. But a national rail strike will have a severe impact on services and on Britain."
At the heart of the row is anger at proposals to cut 1,500 jobs and changes to existing working practices, which the unions claim adversely affect railway safety.
Transport Secretary Lord Adonis said: "A strike is in no-one's interests and could cause serious disruption to passengers.
"Both sides should seek to resolve this dispute by negotiation and not confrontation and I am urging them to do so."
Conservative shadow transport secretary Theresa Villiers said the threat of walk-outs was terrible news for business and travellers.
She added: "The most important thing is that the unions see sense.
"These issues can be resolved via negotiation. It's not fair for the unions to be holding the travelling public to ransom in this way."
Liberal Democrat transport spokesman Norman Baker said the strike was about "putting politics before the passenger".
Commuters give their reaction to the planned rail strikes
He said: "Safety is obviously of prime importance. That is why I wrote to the rail regulator, who told me that it was satisfied that NR's plans will not jeopardise safety, which means that the RMT's claims on safety are simply scaremongering."
The Association of Train Operating Companies condemned the action, saying it would be "hugely frustrating for passengers and bad for British business".
A spokesman said: "It's deplorable for the unions to threaten the first national rail strike in 16 years and shows scant regard for the needs of passengers and an economy which is only just emerging from recession."
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