WINNIPEG -- Manitoba has joined a list of conservative-led provinces challenging the federal government's backstop carbon tax in court.

Premier Brian Pallister says his government will ask a federal court to rule Ottawa has overstepped its bounds.

"Ottawa cannot impose a carbon tax on a province that has a credible greenhouse-gas reduction plan of its own, and we do," Pallister said Wednesday.

He also said Manitoba's court action is separate from those filed earlier in Saskatchewan and Ontario.

"We'll observe other provinces' cases with interest and learn from them, but their cases are not the same as the one we would make."

Manitoba, Saskatchewan, Ontario and New Brunswick refused federal instructions to enact their own carbon levies. That prompted Ottawa to impose its own tax, which started Monday.

The initial rate of $20 per tonne, which works out to 4.4 cents on each litre of gasoline and drives up other fuel costs, is to increase every year until it reaches $50 per tonne in 2022.

Saskatchewan challenged the constitutional authority of the federal government to impose the levy in a court case earlier this year. A ruling is expected in the coming weeks.

Ontario's Progressive Conservative government has a court hearing later this month.

Pallister said Manitoba's challenge will be different because the province had planned to bring in a carbon tax of its own, but at a lower $25 per tonne rate that would not rise each year. The premier dropped that plan when the federal government said it was not good enough.

Liberal MP Terry Duguid, who represents Winnipeg South, said Pallister is taking the wrong approach.

"Carbon pollution shouldn't be a partisan issue. If some Conservative politicians choose to not do what's right for our climate and our kids, we will," Duguid said in a written statement provided by the office of Climate Change Minister Catherine McKenna.

"Instead of wasting taxpayer dollars in court fighting climate action, we would have hoped to see the premier fight climate change."

Manitoba NDP Opposition Leader Wab Kinew called Pallister's court challenge frivolous.

"We know that a court challenge will do nothing to fight climate change in Manitoba, and our children demand better," Kinew said in the legislature.

Two years ago, Pallister obtained a legal opinion from constitutional expert Bryan Schwartz. It said the federal government generally has the right to impose a carbon tax, but could be rebuffed if a province developed its own plan that would be equally effective in reducing emissions.

Pallister said Manitoba's challenge could take two years or more before it is heard, and may not be necessary if the Saskatchewan or Ontario governments win their cases.

He also pointed to the federal election set for October. Federal Conservative Leader Andrew Scheer has promised to revoke the carbon tax if he becomes prime minister.

Pallister would not say whether he will revive the $25 carbon tax he originally planned if the federal levy is struck down.

"We would not need to do that but, at the same time, I don't want to prejudice the legitimacy of our court case by getting into hypotheticals."