Canada's Environment Minister warned on Wednesday that oil and gas companies would be breaking federal laws if they withheld emissions data, after Alberta's premier said the province was considering measures to block a proposed emissions cap.

Alberta Premier Danielle Smith on Tuesday said her government intends to put forward a motion in the provincial legislature that would allow it to launch a legal challenge to Ottawa's proposed oil and gas emissions cap.

Canada's main oil and gas province is also considering looking at other steps to undermine the cap if it becomes law, such as restricting entry into oil and gas facilities in Alberta and access to emissions data.

"If companies stop reporting to the federal government they would be in violation of federal laws, something I certainly wouldn't advise to any large companies," federal Environment Minister Steven Guilbeault told reporters in Ottawa.

The latest spat between Smith's conservative government in Alberta and Prime Minister Justin Trudeau's Liberals highlights the province's staunch opposition to a policy aimed at cutting emissions from Canada's highest-polluting industry.

It also shows how even if Trudeau's government manages to win a federal election next year, the oil and gas emissions cap will face further opposition. Polls currently show the Liberals are on track to lose badly and the opposition Conservative Party has said it would scrap the policy if elected.

The proposed cap would force producers to cut oil and gas emissions 35% below 2019 levels by 2030, and Ottawa says the target can be met using existing technology. But Alberta argues the cap would force companies to cut production by at least one-million barrels per day, nearly a quarter of the province's total oil output.

While Alberta is entitled to challenge federal legislation through the courts, the other measures proposed by the province would be unconstitutional if the oil and gas emissions cap becomes law, said Emmett Macfarlane, a professor of political science at the University of Waterloo.

"Banning federal officials from entering facilities or trying to block disclosure of information regarding emissions ... that is unconstitutional nonsense if the federal government is acting within its authority," Macfarlane said.

"In any conflict between federal and provincial law, federal law wins out."