Hundreds of rail guards and drivers at First Great Western, which operates services in Hereford and Worcestershire, have voted to go on strike after claiming industrial relations had broken down.
Workers at the company overwhelmingly backed industrial action, raising the threat of travel chaos later this month. The executive of the Rail Maritime and Transport union will now consider whether to call strikes over the dispute, which also includes claims that managers are being used to drive and guard trains.
"RMT members have today made quite clear what they think of First Great Western's confrontational style of management," said the union's general secretary, Bob Crow. "The votes reflect the anger that our members feel at the company's behaviour, and if it wants to avoid industrial action it should begin to deal sensibly with the range of issues involved and stop the routine use of managers to guard and drive trains."
The train operator carries more than 60,000 passengers a day on local and long-distance services into London's Paddington station.
Service levels on FGW have been the subject of bitter criticism of late, with watchdog body London TravelWatch calling for First to be stripped of its franchise.
An FGW passenger group is due to meet next week to discuss a possible boycott of services.