Danielle Smith was chosen as leader of Alberta's ruling United Conservative Party (UCP) on Thursday and will replace Jason Kenney as premier of Canada's main oil-producing province.

Smith won 53.77% of the vote from party members and will lead the UCP into the next provincial election scheduled for May next year. She becomes UCP leader with immediate effect and will formally become premier once the province's Lieutenant Governor invites her to form a government.

"I'm back," Smith told a cheering crowd in Calgary. "Today marks a new beginning in the Alberta story. No longer will Alberta ask permission from Ottawa to be prosperous and free."

Smith's most eye-catching policy is a promise to immediately table the Alberta Sovereignty Act, allowing the province to refuse to enforce specific federal laws or policies "that violate the jurisdictional rights of Alberta".

She was the frontrunner to win the leadership race, followed by Travis Toews and Brian Jean.

A former leader of the Wildrose Party and vocal critic of the Kenney government's COVID-19 pandemic restrictions, Smith appeals to grassroots UCP members on the right of the party. Toews, the more centrist candidate, was provincial finance minister until May when he resigned to run for leader.

Alberta is home to the bulk of Canada's oil and gas industry, as well as its vast, high carbon-emitting oil sands.

The new premier comes to power during a record bonanza in energy revenues thanks to soaring global oil prices. Alberta also has a strained relationship with the federal government in Ottawa due to a sense that the federal Liberals' climate polices are damaging Canada's oil and gas industry.

Kenney, a former federal Conservative government minister, had a pugnacious relationship with Prime Minister Justin Trudeau and mounted legal challenges to a federal carbon price and its impact assessment process for major infrastructure projects.

But Kenney's handling of the pandemic undermined his standing among ordinary Albertans and his own party.

The premier managed to antagonise both right-wing Albertans who thought the province should not impose any public health measures to curb the spread of the disease, and those who felt Kenney moved too slowly to introduce restrictions, allowing hospitals to be overrun.

He called a leadership review last year to stave off a caucus revolt, but received only 51.4% of the vote from party members and announced in May he would step down.

Alberta has traditionally been a conservative stronghold and an Angus Reid poll released last week found the UCP lead the opposition New Democratic Party by six points, with 47% of those polled saying they would vote UCP if an election were held immediately. (Reporting by Nia Williams and Kanishka Singh Editing by Josie Kao and Robert Birsel)