BUS engineers have voted overwhelmingly in favour of strike action in a row over pay which could impact on services during the Commonwealth Games
First Glasgow employees voted 98 to 15 in favour of a walkout after being balloted by the union Unite.
An initial offer of a 0.5% increase was rejected by 143 votes to 3 following an earlier ballot.
Members were then offered a 1.2% pay rise in each of the next two years, but Unite asked members to consider strike action.
Union leaders described the vote as a "resounding result" and called on First to get back round the table.
However, the Evening Times revealed yesterday that the bus operator has launched a legal challenge which could force Unite to rerun the ballot.
Unite Regional Industrial Officer, Eddie Duffy, said: "The managing director sent out a letter last week pleading with people not to take industrial action. That can have an effect.
"The email mentioned the Commonwealth Games. They're very worried about a strike. They want to put it off until after the games."
First Glasgow has instructed law firm Eversheds to challenge the legality of the ballot over the official name of the firm given on voting papers.
A source close to the union said: "The ballot described the company as First Glasgow Limited but they say the company is actually known as First Glasgow No 1 Limited and First Glasgow No 2 Limited.
"It's shaky stuff but these things have interfered with industrial action before."
The lawyers are also claiming that the postal ballot period was too short, according to a union source.
If the ballot has to be rerun, the industrial action will be pushed back several weeks, until after the Games.
Unite's Eddie Duffy said: "There's a good chance that that is going to happen. I don't know whether they're doing it deliberately but we're losing all trust in them."
A spokesman for First declined to comment.