Elections Canada has warned environmental groups that running ads about the dangers of climate change during the upcoming federal campaign could be deemed partisan activity.

An Elections Canada official told groups in a training session earlier this summer that since Maxime Bernier, the leader of the People's Party of Canada, has expressed doubts about the legitimacy of climate change, any group that promotes it as an issue in its paid advertising could be considered partisan and might need to register as a third party with Elections Canada.

Elections Canada said the warning applies only to "activities or ads that specifically identify a candidate or party" and cost $500 or more.

"The only place the [Elections] Act covers the promotion of an issue without mentioning a candidate or party is where someone spends money on 'issue ad' during the election period, but the issue must be associated with a candidate or party," Elections Canada said in a statement.

Issue ads could be considered partisan even without referencing a party or candidate if they advocate or counter a position that is clearly associated with a specific party or candidate. Such ads have been regulated during the election period for the last 20 years, Elections Canada said.

Tim Gray, executive director of the advocacy group Environmental Defence, says registering as a third party is onerous for groups like his and could draw unwanted attention from the Canada Revenue Agency, which prohibits charities from engaging in partisan activity if they want to maintain their tax exempt status.

It is "discouraging" that Environmental Defence and other charities might need to revise their messaging about climate change during the campaign period "because one party has chosen to deny the existence of this basic fact," Gray said

"Obviously, climate change is real," he said. "Almost every credible institution on the planet is telling us to get our act together and do something about it."

Last fall, the United Nations Intergovernmental Panel on Climate Change, made up of hundreds of scientists from around the world, said if the world doesn't cut global greenhouse gas emissions by half by 2030, the planet will face irreversible and catastrophic consequences.

Bernier denies 'climate change urgency'

Five of the six political parties expected to have any chance of winning a seat in the upcoming campaign agree that climate change is real and caused by humans. Bernier is the one outlier: he believes that if climate change is real, it is part of a natural cycle and not an emergency.

"There is no climate change urgency in this country," Bernier said in a speech in June.

He also disagrees that carbon dioxide, which experts say is responsible for three-quarters of greenhouse emissions globally, is bad.

"CO2 is not 'pollution,"' he tweeted. "It's what comes out of your mouth when you breathe and what nourishes plants."

Libs can only sell their carbon tax if they lie. <br><br>Lie #1: You’ll get back more money. <br><br>Lie #2: It’s a price on “pollution.”<br><br>CO2 is NOT pollution. It’s what comes out of your mouth when you breathe and what nourishes plants. <a href="https://t.co/4O9Q1lA08O">https://t.co/4O9Q1lA08O</a> —@MaximeBernier

Because of that, Elections Canada is warning that any third party that advertises information about carbon dioxide as a pollutant or climate change as an emergency could be considered to be indirectly advocating against Bernier and his party.

Responding on Twitter, Bernier himself called the Elections Canada rule "absurd."

1/ EC is interpreting a bad law as best it can, but this rule is still absurd. Not because we’re the only party with a different perspective which climate alarmists believe is not legitimate. But because it is arbitrary, draconian, and cannot be applied consistently. <a href="https://t.co/Ha6XM887ap">https://t.co/Ha6XM887ap</a> —@MaximeBernier

Elections Canada said the warning doesn't mean environmental groups are forbidden from giving interviews or press conferences about climate change during the campaign, the spokesperson said.

Rather, it would affect things such as Facebook ad campaigns that cost $500 or more.

"Lots of other activities, such as sending emails or text messages, having a website or canvassing door-to-door about issues raised during the election are not covered by the [Elections] Act, where they do not identify a candidate or a party," Ghislain Desjardins, Elections Canada's senior media relations adviser, said in a statement to CBC News.

"This is true even if the activity promotes an issue that is associated with a candidate or a party."

Audits targeted some environmental charities

Environment groups in Canada are still on edge after being singled out by the Canada Revenue Agency in recent years for their political advocacy, and some fear that if Elections Canada accuses them of being partisan, it will attract another round of audits.

Thousands of protesters flooded the streets this March in Montreal to raise awareness about the dangers of climate change. (Martin Ouellet-Diotte/AFP/Getty Images)

In 2012, the former Conservative government unveiled a $13-million audit program to weed out charities the Conservatives alleged were abusing their tax status by engaging in partisan activities.

The probes went after two dozen environment, human rights, anti-poverty and religious groups — none of them considered partisan — for violating a rule that limited their spending on political advocacy work to no more than 10 per cent of their funding.

The program was launched as the Conservatives labelled some environment groups "radical" and a "threat" to Canada.

The Liberals promised to end what they called a "witch hunt" against civil society groups that opposed the government's policies. It took more than three years, but legislation was changed last year to lift the 10 per cent limitation. The non-partisan rule, however, remains.

Catherine Abreu, executive director of the Climate Action Network Canada, called the Elections Canada warning "shocking."

"Climate change is a scientific fact," she said. "It's not an opinion."

The situation is "contributing to ongoing confusion" about what environmental charities can and cannot do and will give fuel to groups advocating on behalf of the the fossil fuel industry that want to silence their opponents, Abreu added.

Natasha Gauthier, a spokesperson for Elections Canada, told CBC's Power and Politics that any action taken against specific advertising activities would be decided on a case-by-case basis and only if someone made a complaint. She said the decision whether to issue a fine would be made by the commissioner of Canada Elections.