Oceanex says it will divert shipping traffic to handle orders bound for its terminal in St. John's. (CBC)

A lockout of longshoremen in Montreal could have dramatic repercussions for businesses in Newfoundland and Labrador, a government minister says.

Transportation and Works Minister Tom Hedderson said a prolonged lockout could strangle container traffic in the province, and threaten supplies of many things that consumers take for granted.

"Fifty per cent is handled by Marine Atlantic and the other 50 per cent by [shipping company] Oceanex, and their main port of call is Montreal, so obviously 50 per cent of the freight coming in is going through the port of Montreal," Hedderson said.

"Certainly any interruption will certainly cause great difficulty here in the province."

Commercial operations at the Port of Montreal came to a halt Monday morning after the Maritime Employers Association locked out 850 longshoremen in an ongoing labour dispute over a new collective agreement.

Hedderson said he has asked the federal and Quebec governments to bring about a resolution to the dispute.

"You're talking about commodities, you know, like food, construction materials [and] medical supplies, like prescription drugs and so on, so it does have fairly far reaching effects."

Sid Hynes, the executive chairman of Oceanex, said the company has already been diverting traffic to Halifax.

While he doesn't believe a crisis is in the works, he said Oceanex handles materials shipped to department stores, wholesalers, retailers and construction companies, goods that include everything from yogurt to steel for massive construction projects.

"If you see it, we probably touched it," he told CBC News Tuesday. "You name it, it's coming via our services."

On Tuesday, Oceanex diverted one of its ships to Halifax, and has been rescheduling its shipping agenda.

"We started moving as many materials as we can through Halifax," he said.

Hynes said about two thirds of the goods Oceanex brings in to St. John's pass through Montreal