Workers at a shipyard in Prince Edward Island have been ordered to stop engaging in illegal job action.

The provincial Labour Relations Board ordered workers at the East Isle Shipyard to “cease and desist from engaging in an unlawful strike.”

The dispute stems from half a dozen layoffs that took place in March at the shipyard, a division of Irving Shipbuilding, in Georgetown, about 50 kilometres east of Charlottetown.

Soon after the layoffs, the company asked the remaining employees to work overtime to fulfill a contract to complete a tug boat.

In April, 67 of the 90 unionized workers left the yard at noon and did not return to work that day. They also announced that they would refuse to work overtime

The union representing the workers, the International Association of Machinists and Aerospace Workers, told the company if it was short of workers it should rehire those it had laid off.

East Isle said those workers weren't trained to do the specific work needed.

The company filed a complaint with the Labour Relations Board, which ordered the employees to end the work stoppages and agree to work overtime.

In its decision, the board found that what the workers did amounted to an illegal strike. While individuals can refuse overtime, the board said, the union as a whole cannot.

Mary Keith, spokeswoman for East Isle, told CBC News on Wednesday the company is treating this as an isolated incident.

She said the yard is working on three new tug boats and has rehired the employees who had been laid off for one more year.

Representatives from the union did not want to comment. The two sides are in the midst of contract negotiations.