“It is wholly unacceptable that replacement managers can be paid around £500 per shift, about double what our Avanti members earn,” an RMT spokesperson said.
They claimed that it was a repetitive and “destructive approach”, saying it was a reported practice that rewards managers with “instead of resolving disputes”.
“At the heart of the problem is a serious staff shortage, which is why there’s such a heavy reliance on overtime in the first place,” they added.
RMT members had initially planned to strike in the run-up to Christmas, but these plans were called off last-minute.
The union said a revised proposal put to them was rejected by 83% of the 400 members involved in the dispute, before announcing new strike dates.
Avanti said it remained open to working with the RMT to resolve the dispute.