A rail union has warned of potential delays on ScotRail services with its members set to begin industrial action on Thursday.

The Transport Salaried Staffs' Association (TSSA) members will walk out in a dispute over work carried out by driver team managers.

ScotRail has brought in a policy that makes 50 managers cover train driver shifts in addition to their own duties, which a union says leaves them "overstretched and stressed out".

The group's general secretary Manuel Cortes has also criticised the rail firm over "threats to our members" amid the negotiations.

He said: "ScotRail know that from Thursday, trains will be cancelled as our members exercise their lawful right to take part in industrial action but rather than engage in meaningful negotiations, they chose to issue threats to our members.

"They should be hanging their heads in shame as this kind of behaviour has no place in 21st century industrial relations.

"This is entirely a dispute of their making. Firstly, by failing to recruit enough drivers, in an effort to make a quick profit.

"When ScotRail realised they'd need our members to make up for their shortfall they chose to impose changes on our members rather than negotiate with them.

"Every step of the way we have asked them to engage in meaningful negotiations and at every step they have sought to cut us out. They are a disgrace to our railways.

"We are willing to meet with them, anytime, anywhere and we are willing to suspend our action, just as soon as they are willing to guarantee our members won't be forced to drive trains."

Mr Cortes also called on transport secretary Michael Matheson to step in and ensure Abellio, the transport company behind ScotRail, returns to the negotiating table.

However, a ScotRail spokesman said: "We have had numerous meetings with TSSA representatives and we are absolutely committed to engaging with them to reach a resolution.

"ScotRail values each and every member of staff and their hard work to deliver a high standard of service for our customers.

"Any suggestion of bullying is completely untrue and it is very disappointing that the TSSA would wilfully misrepresent our efforts and mislead their members in this way.

"The dispute itself affects only seven people in a company with over 5,000 employees, so any industrial action will have absolutely no impact on services."