Northern has responded to RMT's announcement of a further three days of strike action.
Richard Allan, Deputy Managing Director, Northern, said: “Northern invited RMT to ACAS talks and agreed to discuss the three options RMT had suggested beforehand on the role of the on-board member of staff. Northern was prepared to talk about the RMT's options.
"However, RMT unilaterally changed the basis of what they were prepared to talk about. This is despite the fact that they have reached agreements on similar terms elsewhere in the industry.
"RMT then called yet more strike action which will only cause further unnecessary difficulty for customers. Northern remains ready to talk about the options and calls on RMT to cancel strike action and return to the talks.
"Northern is getting on with the important job of modernising local rail for customers with new trains, better stations and more services. It remains willing to involve RMT in that positive future for colleagues and customers. But progress can only be achieved through talking."