Unite the union has announced that dozens of workers employed by the bus company had voted for strike action over the pay dispute.
The 60 First Glasgow workers, including bus cleaners and shunters, voted by 96 per cent in support of strike action in a ballot turnout of 87 per cent.
Two periods of 48-hour strike action will now take place on May 4-5 and May 18-19.
Unite says the dispute centres on a two year pay deal which would take some workers to £9.48 per hour, backdated to August 2021 to April 2022.
Unite general secretary Sharon Graham said: “That First Bus had the cheek to ‘offer’ two pence less than the current adult minimum wage is beyond insulting.
“This is a business with millions in the bank and comes at time of rapidly rising living costs. I am proud that Unite members have rejected the proposal overwhelmingly.
“First Glasgow would be wise to heed this overwhelming mandate for strike action and get round the table with a serious offer.
“Our members have the full support of Unite in their fight for better pay.”
Wendy Dunsmore, Unite industrial officer, added: “Unite’s members at First Glasgow are determined to take a stand against poverty wages.
“The cleaners and shunters have been forgotten by their employer but they will not tolerate being treated as second class workers any longer. It’s ridiculous that an employer makes a pay offer, even one that’s backdated, which doesn’t even meet the current national minimum wage.”
In December 2021, more than 1300 First Glasgow bus drivers received inflation-busting pay rises of up to 21.5 per cent over two years depending on length of service.
Duncan Cameron, managing director of First Bus Scotland, responded: “We have been notified by Unite of the outcome of a consultative ballot on industrial action with fleet and facilities support members in First Glasgow. We are in negotiations with union representatives and constructive dialogue will continue as part of that process.
“I can confirm all First Bus employees meet current national minimum wage rates.
“Since March 2020, passenger numbers have fallen by nearly a third and have still not fully recovered. As a business, we want to reward and recognise our team members but we have to balance that against rising operational costs we are currently experiencing.”