British Columbia's ports are facing an uncertain future after the longshore workers union rejected a tentative mediated deal and resumed strike action that had been put to a temporary halt only last week.

The International Longshore and Warehouse Union Canada says in Tuesday's decision to go back to picket lines that "employers have not addressed the cost of living issues" faced by workers in the last few years.

The union representing about 7,400 workers who were previously on strike from July 1 to 13 says its priority has always been to protect its jurisdiction, and that position "has not changed."

University of British Columbia professor emeritus Mark Thompson says the situation is now in "uncharted territory" because the strike is unusually long for Vancouver. 

Thompson says the federal government has been very reluctant to enact back-to-work legislation in labour disputes, but strikes disrupting the Port of Vancouver — Canada's largest — have not lasted more than two weeks since at least the 1980s.

The renewed ILWU strike means more than 30 port terminals and other sites across the province are shut down again for an indeterminate time.

The tentative four-year deal that was rejected by the union's caucus had been proposed by a federal mediator at the instruction of Labour Minister Seamus O'Regan.  

A late-night joint statement was released by O'Regan, and Transport Minister Omar Alghabra, confirming the employers' association agreed to the terms of the deal, but the workers' union leadership decided not to recommend ratification of the terms to its members. 

The pair also expressed disappointment, saying that the mediated deal ending the work stoppage was the result of a constructive and substantive collective bargaining process.

The ministers' joint statement also seems to hint at a possible move to introduce back-to-work legislation, stating, "We have been patient. We have respected the collective bargaining process. But we need our ports operating."