Sodexo catering staff picketed Scotland's police headquarters in Fife yesterday in a dispute over pay.
The 20 Sodexo employees, who work at Tulliallan Police College, launched an overtime ban last week over a pay offer of 1%.
The workers, who are members of the GMB trade union, were concerned that Sodexo would draft in staff from other units to cover a special dinner that was held last night because it would undermine the overtime ban.
The GMB is claiming that the workers should receive the Scottish Living Wage of £7.20 an hour. The vast majority of the staff are on a minimum rate of just £6.37.
Richard Leonard, GMB Scotland regional organiser, said the industrial action was "reluctantly" mounted in a bid to peacefully persuade workers not to cross the official picket line and not to carry out work which GMB members would normally do.
"Our members have been told in a memo this week that ‘there will be new faces in the kitchen and service points' and that they should ‘assist them in learning the ropes'," he said.
"They are being asked by Sodexo to saw off the branch they are sitting on and they will not do it. They deserve the Living Wage and they have our 100% backing."
Sodexo has declined to comment.