Railway workers to vote on strike action after union rejects 'derisory' pay offer
The announcement was made ahead of the state-owned operator cutting almost a third of train services to cope with a dispute with the train drivers' union Aslef.
Some drivers are declining to work overtime on rest days while the pay dispute remains unresolved.
The RMT said the timing of its strike ballot would be set out in due course.
ScotRail - which was nationalised seven weeks ago - will begin a temporary timetable on Monday which it said would "give certainty" to passengers during the driver shortage.
It has been roundly criticised for cutting about 700 services per day and the last train on many routes will leave up to four hours earlier than usual.
Hospitality and entertainment businesses fear the cuts wiill affect their income, while commuters could be left struggling to get home using the rail network.
It is believed ScotRail needs 130 new drivers to end its reliance on rest-day working.
A typical ScotRail driver salary is more than £50,000, with drivers being offered a 2.2% pay rise and the opportunity to participate in a revenue share arrangement which would take the total package to 5%.
RMT general secretary Mick Lynch said: "ScotRail needs to put its hands deeper into its pockets and start rewarding their staff properly.
"We are in the midst of a brutal cost of living crisis for workers, but it is still party time for shareholders, speculators and big business executives.
"All we are asking for is a pay award that reflects the value of railway workers and the service they provide to the public day in, day out."
Earlier, Transport minister Jenny Gilruth said that the ScotRail network is dependent on rest day working at the present time .
In an interview with BBC’s Good Morning Scotland, the SNP MSP gave an update on the latest meetings with ASLEF and urged unions to come back to the table.
She added that it was disappointing that a temporary timetable was being introduced as a result of drivers not working on rest days, despite an agreement being in place until October.
She said: “It is absolutely true to say that the network is dependent on rest day working at the present time.
“We need to phase out that practice. I know the unions are supportive of that. It's time for the unions to come back to the table to work with ScotRail.
“I meet with ScotRail on a regular basis as you'll understand ScotRail are the employer, so it's right and proper that they take forward the negotiations with ASLEF and our trade union partners in relation to pay.
"So I think it's hugely important that the trade unions now come back to the table and want to work with them."
She added: “I made an absolute commitment in January to prioritise meeting with our railway unions, they knew I want to work with them on a range of different issues. And they know ultimately, we need to get to a resolution on pay for the benefit of workers, but also for passengers.
Ms Gilruth continued: “Rest day working continues to be needed, as the ongoing training programme for new drivers has been severely impacted by the pandemic.
"An extension to the rest day working arrangements and additional payments for staff was actually negotiated and agreed to with ASLEF, and it continues until October.
“So it's disappointing that this disruption that passengers have experienced over the last two weeks has happened as a result of drivers refusing to work on rest days.”
Training of new ScotRail drivers was impacted by the Covid pandemic, however, it is expected that ScotRail will have an additional 38 drivers trained by the end of the summer, rising to 55 by the end of the year.
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