Luas drivers have rejected a Labour Court recommendation that they should accept cooler bags when forced to take meal breaks away from their usual depot in Dublin.

However, it could be some time into the new year before any real risk of disruption for passengers materialises as the drivers' union SIPTU will have to hold a separate ballot for industrial action, and give at least three weeks’ notice of any planned stoppage.

There is also the potential for further negotiations with senior management of Luas parent Transdev.

If workers were to proceed with industrial action in any form they would lose an annual bonus worth 6.5% of salary or over €3,000 per driver.

The dispute was triggered by the opening of the cross-city extension of the Luas Green Line a year ago.

The change meant 12 out of 67 weekday duties required the driver to take a break in Broombridge rather than returning to their originating depot in Sandyford for lunch which they stored in fridges there.

However, the drivers affected by the new duties argued that under the new arrangements they could not obtain takeaway meals near the Green Line depot during their 30-minute lunch-breaks.

They have dismissed as inadequate improved facilities at the Green Line depot, including vending machines containing subsidised ready meals.

They have also rejected proposals that they should use cooler bags to keep their lunches fresh in the cab of their trams.

The Labour Court said it would not normally concern itself with the function of cooler bags, but ordered an independent assessment of the efficacy of the bags, which found that they would keep food safe for six hours.

Transdev argues that in order to facilitate staff returning to the originating depot for lunch, they would have to recruit five additional drivers at a cost of €250,000 a year - and that under current agreements, no such cost-increasing claims are permitted.

The Luas service employs over 300 workers, of whom over 200 are drivers.