Rail workers on Virgin Trains' West Coast route have voted by nine to one to go on strike in a dispute over pay.
The Rail, Maritime and Transport union said the dispute involves almost 1,800 train managers, on-board catering staff, station and clerical employees.
The union said it was seeking a "suitable and equal" pay offer to one received by drivers, who the RMT said had been given a £500 rise.
RMT general secretary Mick Cash said: "Our members have voted overwhelmingly for action in this ballot which is all about workplace equality and workplace justice.
"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 West Coast franchise covers services from London Euston to Glasgow.
A spokesman for Virgin Trains said: "We are disappointed by the result of the RMT's ballot, but can reassure customers that we will be able to run the majority of services during any industrial action.
"We have offered a 3.2% annual pay increase at a time when the average increase across public and private sector employees is around 2%. We remain open to continuing talks with the RMT."
Members of the Transport Salaried Staffs' Association at the company are currently being balloted for strikes in the same dispute, with the result due on November 28.
The union said it will co-ordinate any industrial action with the RMT.