Members of the RMT are set to take industrial action on Friday.
Staff working on Virgin West Coast services, which includes Milton Keynes, will be taking strike action in a dispute over pay.
The firm has offered drivers an additional £500 on their basic salary to buy out their claim for a one-hour reduction in the base working week without loss of pay.
However the RMT want a “suitable equal offer” to be made to other staff, and claim the firm have “refused point blank to make any serious moves to resolve the issue”.
Further strike action is scheduled on December 22, January 5, January 8, January 26, and January 29.
RMT general secretary Mick Cash said: “Our members are striking for workplace equality and workplace justice. The company have made no serious effort at all to resolve those issues and our action goes ahead exactly as scheduled.
“All our members are demanding is a suitable and equal offer to that given to drivers to buy out their claim for a reduction in the base working week. We have made it clear to the company that the inequality and underhanded approach of Virgin will be fought tooth and nail. We will not accept our members being dealt with less favourably than others.
“The message needs to get through to Sir Richard Branson on his luxury island retreat in the sunshine that those who are financing his lifestyle through their hard graft have had enough and are prepared to fight for justice in their workplaces.
“The union remains available for talks.”
Virgin have been approached for comment.