More than 650 bus workers are being balloted on whether to strike in a dispute over pay.
Members of Unite employed by Arriva in Yorkshire will vote in the next few weeks on whether to launch a campaign of industrial action.
The union said the dispute was over a pay offer of 4.1%, which it pointed out was less than half of the current RPI inflation rate.
Workers being balloted include bus drivers and engineers, based at depots in Selby, Castleford, Dewsbury, Heckmondwike and Wakefield.
Unite said many of the bus drivers were struggling to make ends meet because of the cost-of-living crisis.
The ballot will close on May 23, so strikes could begin in early June if there is a yes vote.
Unite general secretary Sharon Graham said: “This offer is a pay cut and is unacceptable to Unite.
“Arriva has to think again and come back with an offer that fully reflects this cost-of-living crisis.”
Gavin Peace, area operations director for Arriva Yorkshire, said: “While we fully understand concerns about the rising cost of living that workers are facing throughout the UK, it is important that pay offers are affordable and reflect the economic pressures the bus sector also faces at this time.
“Any strike action would needlessly undermine bus travel and cause disruption to the customers and communities we serve.
“We remain keen to reach an agreement with Unite and continue to work towards this. We are aware that the union wish to continue discussion and would encourage them to work with us to find a way forward.”