The P.E.I. Labour Board has ruled MacLean Construction engaged in unfair labour practices when some of its employees attempted to unionize.

In a written decision the board says the company offered employees a pension plan and increased some workers' salaries while the certification process was underway. That's contrary to the P.E.I. Labour Act.

The board had certified the union on March 15 of last year. MacLean Construction appealed that certification on March 27, and held a meeting proposing a pension plan the next day. The company said the meeting was part of ongoing planning that had been underway six months.

The board said it had serious concerns about the company's activities during the review process.

"The concern is increased when, as in the present case, the employer has requested a review of the Certification Order," it said in the written decision.

The board has now upheld the order allowing 21 carpenters and related tradespeople at the company to join the United Brotherhood of Carpenters and Joiners of America, local 1338.

Neither the company nor the union were prepared to comment on the matter when contacted by CBC News.