The company that runs Charleston County school bus fleet is suing the Teamsters, alleging the union is trying to claim jobs not covered under their contract.

Durham School Services LP cited unfair labor practices in a complaint filed in federal court in Charleston this week.

The Teamsters Local 509 of West Columbia represents the company's 400 Charleston County drivers and driver aides, who monitor students during field trips and other outings.

The dispute flared up over the summer, when the union filed two grievances. The Teamsters said Durham was violating their five-year labor agreement by using nonunion employees and contractors to fix bus seats and clean the 350 vehicles.

The company said the grievances were meritless. Durham added the Teamsters had never before objected to its use of nonunion help for the cleaning and repair jobs.

The Teamsters has kept pushing the issue, triggering Tuesday's lawsuit. Durham alleges the union is trying is "seeking to acquire new work" for its members rather than "preserve" the driver and aide jobs covered under the existing contract.

Also, the demand that Durham stop using employees and contractors who don't belong to the Teamsters violates the National Labor Relations Act, according to the lawsuit.

The Warrenville, Ill.-based company is asking the court to rule that its Charleston labor deal doesn't extend to the cleaning and repair jobs. It's also asking for unspecified damages, a jury trial and compensation for its legal costs.

L.D. Fletcher, president of Local 509, said Thursday he couldn't comment on the lawsuit because he hasn't seen it yet. A labor panel was scheduled to review the union's grievances next week, Fletcher said.

Durham also transports students for Beaufort County and the Dorchester 2 School District. The lawsuit pertains only to Charleston County, where the contract between the union and the company runs through Aug. 15, 2017.

The union and Durham have squabbled before in public. Last January, Local 509 voted 186-0 to authorize a strike if its members were unsatisfied with a new labor contract it was negotiating with the company. The two sides struck a deal about two months later.

Contact John McDermott at 937-5572.