The National Labor Relations Board (NLRB) has sued Smithfield Foods to prevent the firm from changing the contractual benefits of some of its unionised employees while the status of those employees' membership is in question.

At issue are those employees who were transferred from Smithfield Packing's South plant in Smithfield, Virginia, which is now closed, to its North plant up the street. The former South plant employees were told they had to drop their membership in Food Processors Local 1046, which represented that plant's workers, and join the Teamsters, which represents the North plant workers. The terms of the two organisations' contracts with Smithfield are different.

The NLRB's regional office in Baltimore last year filed a complaint against the company in the case, alleging that Smithfield engaged in unfair labour practices. The complaint was subsequently amended, most recently in May 2010, according to the lawsuit. A hearing on the complaint now is scheduled to begin in September.

The NLRB wants to stop Smithfield from requiring the transferred workers to accept the terms of the Teamsters contact while its unfair labour practices allegation is unresolved, in order "to prevent the final board order in this case from being meaningless."