Alberta Premier Rachel Notley says British Columbia likely doesn't have the authority to slap a $70-per-tonne tax on thermal coal shipments proposed by B.C. Premier Christy Clark.

Clark, in the midst of a provincial election campaign, has said she wants Ottawa to ban thermal coal shipments from the U.S. as retaliation against new tariffs on softwood lumber imposed by the Trump administration.

If her B.C. Liberals are re-elected next week, Clark vowed Tuesday she will impose a $70-per-tonne carbon levy on thermal coal if the federal government refuses to take action.

Clark said the levy would also apply to shipments from Alberta as well as the U.S. because it wouldn't make sense to single out coal from one place. Notley said she opposes the proposal.

'Bad news' for Albertans

"Of course we are (opposed), and we don't think she actually has the authority to do it," Notley said in response to a question at a news conference in Fort McMurray Wednesday. "And we would argue that of course something that would impact Albertans' export industry like that is bad news for Albertans."

Last week, the United States imposed countervailing duties on lumber imported from Canada. The American lumber industry contends Canadian products are unfairly subsidized.

Notley said the softwood tariff will hurt provinces across Canada. But she suggested that having one province take action against the U.S. on its own could aggravate rather than solve the problem.

"That's why it's really important for us to work together on a pan-Canadian strategy ... where the consequences or the strategies to fight back are also considered in the context of how it impacts all provinces, and it's not just how it impacts one province," Notley said.

Thermal coal is burned for heat and electricity. Clark's proposed tariff wouldn't apply to metallurgical coal that is used to make steel.

It's not the first time Alberta and B.C. have engaged in interprovincial trade disputes. The provinces have clashed in the past over the Northern Gateway pipeline, that would have stretched from Alberta through B.C. but was rejected.

'A tax grab': Edson mayor

Greg Pasychny, the mayor of Edson, said he sharply opposes any tax on thermal coal shipments — especially since the coal mine south of the town is one of its biggest employers.

"It's a tax grab — there's no other way of looking at it," he said Wednesday. "It's B.C. trying to get more money off of Alberta."

Pasychny said it's unfair for B.C. to pose a tax because Alberta doesn't have a port from which to ship. He said the tax will hurt the entire country.

"Sometimes you want to bang your head against the wall when you consider that we're all part of one nation," he said. "All you're doing is hurting your country."