Thousands of Network Rail maintenance workers will strike today in a row over jobs and conditions.
The Rail Maritime and Transport union said up to 12,000 of its members would walk out for 30 hours from 12 noon, warning that the action would have a “cumulative” effect.
NR insisted there would be no impact on services.
RMT general secretary Bob Crow said he expected the strike to receive “rock solid” support, adding: “The company has turned a dispute about harmonisation into an attack on jobs and conditions.
“The weekend’s strike will be a demonstration by our members that they expect talks about harmonisation to produce proposals about harmonisation, not ever-longer lists of the conditions the company wants to destroy.
“After months of fruitless talks the company has finally let the cat out the bag and is talking about a reduction in numbers of people employed, and our members have made it clear that they will resist that attack.
“Our members’ hard work and the £400 million in efficiencies they have already made have allowed NR to report pre-tax profits of more than £3 billion over the last two years.
“It is on the back of our members’ hard work that the top bosses have awarded themselves huge bonuses, yet they are telling us they can’t afford real harmonisation.
“If Network Rail wants to settle this dispute it should get around the table and negotiate a harmonisation package that is acceptable to our members.”
NR took maintenance work back in-house four years ago from seven private companies and inherited more than 50 different sets of terms and conditions.
The company said the union had been making “ridiculous” demands including putting all workers on a 34-hour working week and increasing pay by “massive” sums, which would add over £100 million to the maintenance wage bill.
An NR spokesman said: “We have enough fully qualified and competent people to carry out the time-sensitive day-to-day maintenance work over the weekend. Non-time-sensitive work will be rescheduled
“The people undertaking this work at the weekend are the maintenance teams’ supervisors and managers who are already the experts in this field.
“Her Majesty’s Railway Inspectorate have been fully briefed and involved in our contingency plans and have raised no objections.”