SCOTRAIL bosses have warned strikes set to start next month are likely to have a “severe” impact on the network.

More than 40,000 members of the Rail, Maritime and Transport union across Network Rail and 14 train operating companies will walk out on December 13, 14, 16 and 17 and on January 3, 4, 6 and 7.

Phil Campbell, the head of customer operations at the nationalised rail firm, said: “While this dispute does not involve ScotRail staff, it will have an impact on our ability to provide services as the RMT planned action will involve Network Rail staff in Scotland.

“We’re currently assessing the full impact of this planned strike action, and will update our customers as soon as possible.”

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As part of the RMT strike, its members will not work overtime from from December 18 until January 2, meaning RMT members will be taking industrial action for four weeks.

ScotRail said the impact on passengers in Scotland was “likely to be severe”.

Mick Lynch, the RMT’s general secretary, said the latest round of industrial action would “show how important our members are to the running of this country and will send a clear message that we want a good deal on job security, pay and conditions for our people”.

The strike includes crucial signalling staff, and previous strike action had left only skeleton services operating north of the border.

Mr Lynch said apologised to passengers for inconveniencing them, but said he urged they “direct your anger and frustration at the Government and railway employers during this latest phase of action”.

“Working people across our class need a pay rise and we are determined to win that for our members in RMT,” he said.

Tim Shoveller, Network Rail’s chief negotiator, said “no-one can deny the precarious financial hole in which the railway finds itself” and that “striking makes that hole bigger and the task of finding a resolution ever more difficult”.

“Only through reform, that will not result in anyone losing their job, can savings be made that can then be converted into an improved offer,” he said.

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“While progress has been made over these last two weeks, we still have yet to find that breakthrough.”

Graham Simpson, the Scottish Conservatives’ transport spokesman, said the prospect or more strikes from the “militant RMT union is the last thing that long-suffering passengers need”.

“For a moment, it looked as if they might offer us a respite from their plans to wreck Christmas but, true to form, they’ve been unable to resist their destructive approach,” he said.

“Thousands of hardworking rail staff have no desire to inflict further misery on passengers, but they are being let down by their extremist leadership.”