ScotRail has warned customers of significant disruption to services over the next six Sundays, after rail union RMT confirmed strike action over an ongoing payment row.

The union said that conductors will go ahead with strike action in a fight for “equality and justice over enhanced payments for rest day working”, starting this weekend due to the row over payments for rest day working.

More than 75% of members voted to strike and it has instructed them not to book on for any shifts that start on Sunday March 28, April 4, 11, 18 and 25 and May 2.

The union said it will give notice of further Sundays of action if no agreement is reached with the company.

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Its general secretary Mick Cash said: “I have no doubt that our ScotRail members will show full support and stand shoulder to shoulder during the days of industrial action.

“It’s frankly disgusting that rather than recognising the issues at the heart of this dispute the company have resorted to disgraceful mud slinging.

“Staff at the front line who have put themselves at huge risk during this pandemic will take no lectures from company bosses who have kept themselves well clear from danger.

“We have made it clear that we will not allow ScotRail to divide the workforce and are demanding that ScotRail do what is fair and honour an enhanced rate for rest day working for all grades.”

The union also said all its Abellio ScotRail conductor members are instructed not to work any rest days or undertake any higher grade duties from 12.01am on Friday until further notice.

ScotRail said the strikes are a bid to force an increase in overtime payments at a time when ScotRail is facing its worst ever financial crisis.

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A number of services on key routes will be cancelled as a result of the action.

It said there will be limited bus services for key workers to University Hospital Hairmyres in East Kilbride, Queen Margaret Hospital in Dunfermline, and Victoria Hospital in Kirkcaldy.

Graham Ralston, ScotRail head of conductors, said: “The strike action will have no impact on ScotRail’s position on overtime pay increases, given the severe financial challenges we face.

“The strike is wrong during a global pandemic and will have a significant impact on those who need to make essential journeys.

“We will do everything we can to minimise the consequences of this action, but key workers will be adversely affected. Inevitably, many will have to find alternative and much less convenient ways to get to work to perform their life-saving duties.”