ScotRail workers are to launch a fresh wave of strikes in an ongoing row over driver-only trains.

The rail union is planning six days of strike action, including two 48-hour walkouts throughout July.

Members of the RMT union were already due to take strike action over the long-running dispute but extra dates have now been added.

The union announced strikes will be held on July 3, 10, 11, 14 and over the weekend of July 16 and 17.

Industrial action has already been held and the conciliation service Acas has been involved in trying to resolve the dispute but it remains deadlocked.

The union said it was defending its policy of no extension of driver-only trains (DOO) and for guards to be in control of operating doors.

RMT general secretary Mick Cash said: "Despite a series of rock solid strikes it is extraordinary that Abellio/ScotRail continues to ignore the strength of feeling amongst their staff over the extension of DOO.

"That disgraceful and cavalier approach to jobs and safety on Scotland's railways now leaves us with no choice but to move to a new phase of industrial action.

"Our members on ScotRail stand determined and united in this fight for jobs and safety on Scotland's rail services.

"The workforce knows that any extension of DOO is a clear attack on our members hard-earned terms and conditions.

"RMT members should not have to face the risk of their role and responsibilities being reduced and undermined.

"The workforce also knows only too well that there is a very real threat to passengers of watering down and wiping out the safety critical role of the guard on these ScotRail services.

"That is a lethal gamble with basic rail safety."

A Transport Scotland spokesperson said: "The announcement of this new wave of strikes is disappointing as our absolute priority throughout this process has always been safety and encouraging a swift and satisfactory resolution to this dispute.

"The Transport Minister has met with the RMT to discuss their concerns and encourages both sides to get round the table and discuss a way forward that will put an end to passenger disruption.

"The ScotRail franchise contract mandates that a second member of staff is on every train service, and only in exceptional circumstances would a train run without one.

"Passenger safety is central to the operation of our railways which is why the Transport Minister has written to the ORR to seek assurances over the safety of DCO use on trains in a Scottish context, which were forthcoming."