Liberal Leader Justin Trudeau has vowed to pursue a national carbon pricing plan to combat climate change if he becomes prime minister, proposing a medicare-style model in which Ottawa would set national targets and enforce principles but allow provinces to design their own systems.

The Liberal Leader launched his climate policy – which will be a major plank in his election platform – during a speech on Friday at Calgary's Petroleum Club, where he acknowledged the spectre of his father's highly interventionist National Energy Policy lingers.

He slammed Stephen Harper for failing to lead on climate policy, saying the Prime Minister has given Canada a black eye internationally, which has hurt the industry's efforts to build pipelines to transport crude. And he said the New Democratic Party would impose a "one-size-fits-all solution from Ottawa" with its proposed cap-and-trade approach.

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Mr. Trudeau is attempting to walk a fine line: supporting pipelines and the growth of the oil sands industry while insisting the country needs federal leadership to fight climate change. He is also leaving the key details of any national system – whether there would be a minimum price for emissions of greenhouse gases, how Ottawa would enforce its standards – to a first ministers' conference that would not occur until after the election scheduled for October.

But he made it clear his plan would put a price on carbon, and that all provinces would be expected to pay their share.

"Many in this room believe that a price on carbon is good for the environment, for the economy and for Alberta's oil and gas sector," he told a business audience, noting many companies already operate with an assumed carbon price. "You know Canada needs to have a price on carbon."

He cited policies in British Columbia, Alberta and Quebec, and noted that Ontario will soon introduce some form of price on carbon, either through a tax or a cap-and-trade system similar to Quebec's.

"Canada needs to show the world that it is serious about addressing carbon emissions and reducing them, and we will do that in a way that is consistent with the strengths and objectives and capacities of various provinces," Mr. Trudeau said in a phone interview. Asked whether that would include a national floor price for carbon, he said: "Yes, the hope is we will be able to work that out with the provinces."

The Liberal Leader said he would work with the provinces to establish carbon-reduction goals, and travel to the United Nations climate summit in Paris in December, where countries hope to conclude a climate treaty. Within 90 days of that summit, he would meet with premiers and territorial leaders to hammer out a national plan.

NDP deputy leader Megan Leslie said Mr. Trudeau is offering "nothing but platitudes and vague promises."

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"It is clear that Mr. Trudeau has no plan for balancing the environment and the economy," she said in a statement.

Environmentalists welcomed Mr. Trudeau's focus on climate change but questioned his support for pipelines and oil sands expansion. To meet Canada's international climate obligations, most oil sands reserves must stay in the ground, said Louise Comeau, executive director of the Climate Action Network.

Mr. Trudeau insisted an ambitious climate policy is not inconsistent with supporting oil sands expansion. "If we set serious emission targets, then everything else falls into place and the expansion of the oil sands will be done in a way doesn't interfere with us meeting our targets."

"Engaging the provinces is overdue and sorely needed," said David McLaughlin, former president of the National Roundtable on the Environment and Economy. But the Liberal plan is risky because it assume provincial premiers will co-operate on an issue fraught with divisive economic and political pitfalls, he added.