The Canada Industrial Relations Board has ruled that a renewed strike by dockworkers in western Canada is illegal, but their union is not giving up.

The International Longshore Workers Union Canada responded by giving 72-hour notice to restart their work stoppage legally.

The move comes a day after ILWU, which represents workers across ports in British Columbia province, tore up a tentative agreement that halted a previous strike that lasted 13 days.

The renewed strike action will begin on Saturday morning, according to the BC Maritime Employers Association, which is made up of shipping companies and terminal operators.

“The reissuance of strike notice shows that we will be facing a repeat of actions by the ILWU Leadership that will continue to grind operations to a halt at Canada’s largest ports,” the group said.

BCMEA said bulkers will not be affected by the strikes, and it intends to continue to service cruise ships.

But in the 22 days since the union gave its first strike notice, the labour strife has disrupted CAD 10bn ($7.6bn) in cargo, the employers claim.

ILWU president Rob Ashton contended on Wednesday that the strike was not a renewed action, despite the employers’ complaint to the Industrial Relations Board that 72 hours’ notice was required before a return to the picket lines.

“The ILWU has been in a legal strike position since July 1, but suspended picketing at the request of the Minister of Labour while the ILWU considered a collective agreement with settlement terms suggested by a mediator,” he said.

“As required by our constitution, the ILWU contract caucus considered the tentative contract in a two-day meeting. The caucus was not satisfied the mediator’s deal met the membership’s goals and directed the bargaining committee to seek a negotiated agreement. ”

He said that the ILWU regrets the economic impact of the strike, but the board’s order will only make lead to longer industrial action.

The strife across the West Coast, including the nation’s largest port, has raised the spectre of further federal government action to keep ports open.

“We once again ask the government to allow free collective bargaining to occur and allow the longshore workers to use the options allowed by the Canada Labour Code,” Ashton said.