Norbert Dentressangle (ND) employees in the UK have rejected the company's initial proposals for its pay and conditions package for 2009-2010.
This includes pay and hours, although the firm says it is too early to divulge any details.
A company spokesman says: "We are currently in the process of the annual negotiations between the company and the union (Unite ). The first round of voting has been to reject the company offer - therefore negotiations are continuing."
He adds that only the transport arm of the UK business is affected. Unite was unavailable to comment.