Striking workers at a Vale Inco nickel mine in Sudbury have taken their fight against the miner to Ontario's Labour Relations Board.

In July, thousands of workers at the Brazilian mining conglomerate's Sudbury operations walked off the job. At the start of October, the company restarted some operations with replacement workers.

Workers picket the Vale Inco smelter complex in Copper Cliff, near Sudbury, Ont., in July. The company reopened its Sudbury-area operations using non-union staff in October. (Gino Donato/Canadian Press)

On Monday, United Steelworkers lawyer Rob Healy told the board the company has undercut the union's capacity to enforce a strike by forcing some non-striking members to do the work of picketing employees. Vale Inco's actions have had a "chilling effect" on the strike by forcing members of Local 2020, which represents office workers, to do the tasks of mill workers and miners.

The board is an independent, quasi-judicial tribunal designed to mediate labour disputes in the province.

Healy said the company's actions have created an "inherently hazardous workplace."

The union asserts that members of Local 2020 were asked to do the work of striking employees under threat of discipline from the company, and this means the union can't prevent the employees from doing the work.

Vale Inco said about 50 workers have been asked to fill in while other employees are on strike.

Vale Inco lawyer Tim Liznik told the labour board the union is asking the regulator to enforce rights established in the collective agreement of the striking Local 6500, a contract which expired before the strike began.

The company said it has the right to replace striking employees however it can, including using non-striking union members.

Liznik argued that the office workers in Local 2020 don't have a provision in their collective agreement preventing them from doing additional work, so there is nothing stopping the company from asking them to take on the work of their striking colleagues.

He added that 2020's collective agreement does give the employees the right to refuse work they feel is unsafe.

Battle spreads

Last week, the union took its fight against the miner to Europe. A union delegation organized protests in Germany and Sweden, urging Vale customers to cease doing business with the firm until the labour dispute ends.

At issue is Vale's proposal to reduce a bonus tied to the price of nickel. In addition, workers oppose a plan by the company to exempt new employees from its defined-benefit pension plan, which guarantees employees a reliable and steady income after retirement.

The company is proposing to provide them with a defined-contribution plan, which bases retirement benefits on investment returns.

In total, more than 3,500 Vale Inco workers in Sudbury, Port Colborne, Ont., and Voisey's Bay, N.L., have been on strike since July. Theirs are the first job actions at the company since Vale bought Inco's assets for $19 billion US in 2006.

With files from The Canadian Press