A bitter political debate is stirring among Quebec's two main political parties over western Canadian oil being exported to the world through the province.

Oil shipments on the Saint Lawrence River are increasing this fall and could more than double in four years.

The opposition Parti Quebecois is slamming the Liberal government for allowing the oil into Quebec, saying the Liberals don't have guarantees on either jobs or environmental safety.

The PQ hit back, saying that when the PQ was in power last term, it encouraged an Enbridge pipeline reversal to bring Alberta oil to Quebec.

That was different, said PQ energy critic Bernard Drainville.

“Let's not mix up two things. We have one project, it's for Quebec's consumption needs and it's going to be maintaining, creating jobs in Quebec,” he said.

This new project by Transcanada would bring supertankers through the Levis terminal and up the coast to a new terminal to be built in Cacouna. Up to 150,000 tonnes of oil per day would be shipped in, much of it for export to foreign markets.

The PQ said that is too risky and since marine transport is a federal domain, it's out of Quebec's control.

“Hey, look, the Saint Lawrence River is the main reservoir of drinking water for the population of Quebec,” said Drainville.

Former premier Pauline Marois wanted oil, said energy minister Pierre Arcand.

“She wanted Quebec to be a place where we had a lot of petroleum so I'm always astounded to see how they react,” he said, adding that the Liberals too have lots of questions about the oil shipments.

“We want to make sure that there are enough economic benefits in that project. We want to make sure that from an environmental standpoint it's a good project,” said Arcand.

How much to charge oil companies for using Quebec to export oil is the next battle, with politicians arguing about royalties – what is a fair price considering the potential risks – and gains.