Image copyright Getty Images Image caption Ms Notley is not the subject of any criminal investigation, but has faced threats of violence since she was elected in 2015

Canadian politicians have expressed outrage after protesters at a political rally chanted "lock her up" about Alberta Premier Rachel Notley.

Protesters erupted into jeers at a rally against a carbon tax, hosted by the right-wing Rebel media group.

"Lock her up" was frequently chanted by Donald Trump supporters in reference to Hillary Clinton during the US election.

Mrs Clinton was under FBI investigation over her emails but Ms Notley has not faced any criminal probe.

But the New Democratic Party leader has been subject to threats of violence since her election in 2015.

The crowds began shouting the phrase outside the province's legislature on Saturday at a rally over the provincial government's planned carbon tax.

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The rally was organised by Rebel Media, an online news and right-wing opinion outlet.

Conservative leadership hopeful Chris Alexander, who was criticising Ms Notley in a speech when the shouting began, said he was "shocked" and mortified" by the chant.

Media playback is unsupported on your device Media caption Trump's turnabout from 'lock her up' to no prosecution

But Mr Alexander has since come under fire for not immediately intervening at the rally.

A video of the incident appeared to show Mr Alexander cracking a smile and gesturing with his finger when the chanting began.

The former immigration minister told a CBC News programme he did not interrupt because he was "trying to find a moment to interject with what I thought was the real conclusion of what this discussion was".

He added he wanted to change the chant to "vote her out".

Interim Conservative Leader Rona Ambrose condemned the incident as "inappropriate and unoriginal".

"We don't lock people up in Canada for bad policy, we vote them out," she said.

"I don't know what to say - it's people acting like idiots."

Conservative Party Leadership Candidate Deepak Obhrai also weighed in on the rise of intolerance trickling into Canadian politics.

"We're witnessing Trump-style politics invading Canada," Mr Obhrai, a Calgary-area MP said.

"It is the responsibility of event organisers that they distance themselves from hate-mongering and insults. Otherwise we all lose."

Image copyright Getty Images Image caption "Lock her up!" became a war cry for many Trump supporters on the campaign trail

Protesters invoked a slogan often shouted by supporters of president-elect Trump, who accused Mrs Clinton of criminal wrongdoing in her use of a private email account while at the State Department.

An FBI investigation concluded that while she was "extremely careless", her actions did not warrant criminal prosecution.

Still, the phrase became a rallying cry for many Trump supporters.

Ms Notley's NDP-led government has planned to introduce a broad-based carbon tax on gasoline in a conservative province struggling with a downturn in the oil sector.