A wave of industrial action is ­threatening to bring widespread disruption to the Commonwealth Games.

Unions representing transport ­workers and staff who run sports venues and key attractions are to ballot members in a long-running row over pay and conditions for working during the event.

After months of talks, the threats last night brought the prospect of industrial action closer.

Three unions, which have about 1000 members in Glasgow Life - the body that runs Glasgow's municipal museums, galleries and sports facilities - have been locked in negotiations with management.

They claim staff faced with working overtime, early morning and late ­evening shifts will receive no more than their flat rate of pay, with the only sweetener an early finish on Christmas Eve.

Union sources claim that while potential industrial action includes work-to-rule and an overtime ban, there is a preference among some workers for a one-day stoppage.

The action could potentially shut the famous Kelvingrove Art Gallery and Museum, the new Riverside Transport Museum and the Burrell Collection on the south side of the city.

Sources within Glasgow Life said that on the basis of their number crunching they were confident even a one-day walk-out could be managed by the trust. They also played down disruption to Glasgow 2014 venues, citing lack of militancy within that section of the workforce and claiming staff at places like the Velodrome and National Indoor Arena were "up for the Games".

A ballot by Glasgow City Council trading standards and environmental health staff, whose leave has been cancelled in the run-up to the Games, closes on Monday, with the prospect growing of a knock-on effect on inspections of food outlets, hotels and even pubs in the run-up to the event.

Meanwhile, hundreds of bus and Subway workers are to be balloted for industrial action in a row over pay that may impact on public transport arrangements at the Games.

Unite said it was conceivable that if Strathclyde Passenger Transport (SPT) and FirstGroup workers voted for industrial action over what it called "derisory pay and working practices" it would affect the event.

SPT said it was "incredibly disappointing that Unite is threatening to jeopardise transport arrangements during the largest multi-sport event Scotland has ever hosted".

Some 150 FirstGroup bus engineers and 270 Subway workers will be balloted for a strike, or action short of an all-out stoppage on June 30, with a result expected later that week.

If workers vote in favour of action, the union has to give seven days' notice before a strike and has 28 days from the date the ballot closes to use any strike mandate. The opening ceremony of the Games is on July 23.

A Unison spokesman said: "Glasgow Life workers who work overtime to deliver the Games and have had leave restrictions placed on them should be afforded similar arrangements to workers in the council or other arm's-length organisations."

A Unite spokesman said: "There is a resolve within Unite and across the three unions but we hope a resolution will be found. No-one wants disruption during the Games."

A spokesman for Glasgow Life said: "We're confident that the majority of our staff are looking forward to being part of what promises to be a once-in-a-lifetime opportunity, as we welcome the world to Glasgow. The feedback we have received has been incredibly positive and staff in areas not directly involved in the Games have been volunteering to take up roles during Games time."

The unrest among SPT Glasgow Subway workers comes after they were told they would receive no payment for the increased work and flexibility demands during the Games, while being expected to push on with "unpopular shift patterns", Unite said.

Some 150 FirstGroup bus engineers based in Glasgow are in dispute over the company's 2014 pay offer of 0.5% with a further 0.4% on the basis of accepting an inferior pay allowance, said Unite. This makes them the "poor relations of the First Bus family in Scotland", according to the union.

Meanwhile, it emerged thousands of First ScotRail staff on duty during the Games will receive extra pay of up to £275 in "recognition and reward" payments for work through the Commonwealth Games after union negotiations. A similar deal was struck for the London 2012 Olympics, when workers were paid hundreds of pounds in extra bonuses.

An SPT spokeswoman said: "We would urge Unite to consider the impact on customers and potential damage to Glasgow's welcoming reputation and call off the ballot."

She added: "It is simply not true that staff will lose out on pay. SPT has made it clear that any Subway staff requested to work additional hours will be paid in line with their current terms and conditions."

Fiona Kerr, managing director of First Glasgow, said union officials had a "clear unwillingness to engage in meaningful talks" and that she had concerns they had failed to properly consult with their members.