The Ontario Labour Relations Board has ruled that members of Unifor engaged in unlawful strikes in their efforts to protest the planned closure of the General Motors assembly plant in Oshawa, Ont.

The ruling orders the union and its members including president Jerry Dias to cease and desist from engaging in, authorizing or counselling unlawful strikes.

General Motors Canada filed an application with the board seeking to stop "any further illegal activities" after several job actions by union members following the news that the Oshawa plant was closing.

Unifor said in its response that it denied any violations of the law and that the cited incidents were discrete and resolved quickly.

GM's allegations focused on several incidents where union members halted work or engaged in demonstrations, including on Nov. 26, when the company announced the closure, and Jan. 9, when it confirmed it would not reconsider its decision.

The ruling also covers actions by employees at auto parts suppliers Inteva and Lear, who temporarily walked off the job in separate actions protesting the GM Oshawa closure.