US-based Sodexho-Marriott Services has been ordered to post notices at its 10,000 sites in the USA informing employees of their right to talk to one another about their pay and conditions.
According to the US Hotel Employees and Restaurant Employees International Union (HERE), its staff were not allowed to do so. It has told Sodexho-Marriott to put up notices telling the workers otherwise.
Marty Leary, East Coast research co-ordinator for HERE, said: "At thousands of work sites across the country workers have been effectively muzzled."
Sodexho-Marriott denied it had any such rules in place. It said its workers had always been free to talk to each other.
The company said it had been asked by the National Labor Relations Board to revise the language in its employee handbook in order to clarify two points.
One related to confidential company information, which it calls "proprietary information". A spokesman for the group said: "We have added that proprietary information does not include information related to wages, benefits or hours of work.
"If a person wants to tell someone what they are making, we want them to be able to." He added: "They were always allowed to talk about their pay and conditions, but it was not stated that they might."
In Britain, Sodexho and Marriott said their staff could talk to each other about their pay.
Dave Turnbull, regional organiser at the Transport and General Workers' Union, said he had never seen a contract forbidding an employee to talk about such matters. He said: "My understanding of international law is that it does allow people to talk to each other."
By Louise Bozec