Bus staff at Arriva in Merseyside and Greater Manchester are balloting for strike action in a row over pay.
Over 1,800 members of the Unite union are involved in the dispute.
If workers vote for industrial action then strikes could begin in July.
It comes as many parts of the north west are due to be affected by the biggest rail strike in 30 years this week.
Unite general secretary Sharon Graham said: "Arriva can full afford to pay our members a fair rate of pay but it is choosing not to do so to boost its profits."
Unite says the dispute follows the company offering staff a "pitifully low pay increase" that involved a "maximum no strings pay increase" of 3%, or a 6% increase which "includes reductions in sick pay and loss of Saturday enhanced pay".
It added that both offers are "far below" the current real inflation rate of 11.1%.
The depots involved in the dispute are: Birkenhead, Bolton, Bootle, Liverpool, Macclesfield, Manchester, Runcorn, Southport, Speke, St Helens, and Winsford.
The union says pay rates for bus drivers vary between the various depots with drivers at Winsford paid just £11.08 an hour.
Unite regional officer Dave Roberts said: "Strike action would result in considerable disruption for passengers throughout the North West but this dispute is entirely of Arriva’s own making.
"Despite extensive negotiations it has failed to make an offer which is anywhere close to our members’ expectations. "Even at this late stage strike action could still be avoided if Arriva returns to the negotiating table and makes a realistic pay offer."
An Arriva spokesman said: "We are fully committed to reaching an agreement with Unite for our North West staff and talks are ongoing." The ballot will close on Monday 4 July.