The battle over pipelines has turned into a war of words.

Calgary mayor Naheed Nenshi spoke out Friday, harshly criticizing John Horgan over an article the B.C. premier wrote for the Medium website in April.

“It’s very clear that Mr. Horgan, who I think is one of the worst politicians that we’ve seen in Canada in decades, he appeals to populism in a way that is not based on fact,” said Nenshi to a reporter in Calgary. Tweet This

The article was about Horgan’s visit to the Heiltsuk First Nation after the grounding of the Nathan E. Stewart tugboat, which spilled more than 100,000 litres of diesel fuel into the waters near Bella Bella.

Horgan’s article was published the same weekend he met with Alberta premier Rachel Notley and Prime Minister Justin Trudeau in Ottawa about the Trans Mountain pipeline expansion.

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“The diesel slick was everywhere you looked, and the smell from the fumes was overwhelming. From our small boat, we watched the waves push diesel over clam beds that had been harvested by the Heiltsuk for centuries,” reads the article.

“The community had been working for days alongside emergency responders to try and contain the spill and protect the clam beds. People were exhausted, and beside themselves with grief. The devastation I saw that day is considered by some to be a small spill, yet the Heiltsuk will live with the consequences for many years to come.”

WATCH HERE: Trudeau, Horgan and Notley talk pipeline politics in Ottawa

2:07 Trudeau, Horgan and Notley talk pipeline politics in Ottawa Trudeau, Horgan and Notley talk pipeline politics in Ottawa

The $7.4-billion Trans Mountain pipeline expansion project would see nearly three times as much crude moved through pipeline from north of Edmonton to the Kinder Morgan facility in Burnaby.

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“I wonder if he understands every single vessel that goes through every single coastal water in British Columbia has a gas tank and that tank has diesel in it and it’s single-hulled,” said Nenshi.

“So unless he’s planning on stopping every single boat from going through the waters, diesel spills have nothing to do with what we’re talking about here. Bitumen in double-hulled tankers is not the same as a gas tank on a tugboat.”

The expansion would also see tanker traffic increase seven-fold. The B.C. government is waiting for the B.C. Court of Appeal to rule on whether the province has the jurisdictional right to restrict the flow of bitumen by pipeline or rail.

Horgan’s office said the premier is unavailable to respond to Nenshi’s comments. The attack comes the day after former U.S. Vice President Al Gore spoke out against the pipeline expansion.

The Kinder Morgan pipeline carrying dirty tar sands oil would be a step backward in our efforts to solve the climate crisis. I stand with @jjhorgan, @MayorGregor, and all of the Canadians – including the First Nations – who are fighting to stop this destructive pipeline. #StopKM — Al Gore (@algore) May 10, 2018

A recent poll from the Angus Reid Institute found that a majority of British Columbians and Canadians were in favour of the pipeline expansion.

But 74 per cent of people who responded to the poll said they are very or moderately concerned of the risk of an oil spill or accident from a tanker carrying oil through the waters off Metro Vancouver.

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READ MORE: Support for the Trans Mountain expansion grows amidst pipeline dispute

“He knows he’s not going to win in court, he knows he’s not going to win the point of public opinion. He’s hoping to scare away the investors,” added Nenshi.