Hundreds of ScotRail workers could walk out in September unless they receive a “credible” pay offer, a union has warned.

Unite, which represents more than 300 workers at the publicly-owned railway operator, has become the latest union to announce a strike ballot for its ScotRail workers in a dispute over pay.

It says its members, who include train cleaners, engineers, ticket agents, hospitality assistants and conductors, are yet to receive a formal and fair pay offer from the employer.

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The ballot will open on Wednesday and run until August 20, the union said.

Unite general secretary Sharon Graham said: “Unite has no option but to ballot our members across all grades. Disgracefully, ScotRail has not even made a formal pay offer let alone a fair one for our members.

“Unite’s members are essential to keeping the trains running, yet many of them struggle to survive financially as they don’t earn huge sums of money. They have Unite’s full backing in the fight for better jobs, pay and conditions.”

Unite industrial officer Pat McIlvogue called on ScotRail and the Scottish Government to take action to avert potential strike action.

“ScotRail must formally table a credible pay offer which our members can seriously consider before this dispute escalates into nationwide strike action,” he said.

“The Scottish Government, who are the ultimate paymasters, and ScotRail need to get their heads together and quickly.

"There is still a window of opportunity to resolve this dispute through negotiation. If they fail to grasp this chance, then it will be full steam ahead towards autumn strike action.”

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The Aslef and RMT unions recently announced they will also be balloting their ScotRail staff on strike action in a dispute over pay.

Transport Scotland and ScotRail have been contacted for comment.