The fight inside First Group buses could spread rapidly with new strike ballots in Yorkshire and Glasgow.
These come as strikes in Weymouth against First Dorset and First Hampshire buses enter their sixth week.
The workers are members of the Unite union.
Unite has announced a strike ballot of 4,000 workers in Yorkshire.
It covers workers in Bradford, Doncaster, Halifax, Huddersfield, Rotherham, Sheffield and York. They face attacks on pay, terms and conditions.
Meanwhile, Unite members at First Glasgow voted overwhelmingly for strikes over driver shortages in a consultative ballot last week.
The ballot covered some 1,700 workers.
More than 110 drivers in Weymouth were set to strike for three days both this week and next in their fight over pay.
The Weymouth drivers are the lowest paid in First Group throughout England. Yet bosses refuse to budge despite a profit of £52 million across First’s UK-wide bus division last month.
First have removed check off for union dues, so workers are converting to direct debit.
They collected £1,300 for the dispute at the Tolpuddle festival.
Thanks to Tim Nicholls