Bearing posters of Justin Trudeau’s face, written over with green crosses and the word “pipeline”, students gathered in front of the Canadian prime minister’s Montreal campaign headquarters.

“Three steps forward, three steps back, that’s government policy,” they chanted. They were railing against what they consider deficiencies in Trudeau’s environmental policy.

The nationalisation of an oil pipeline in 2018 is one of the major criticisms levelled against Trudeau, who is seeking re-election in Canada’s election on Monday.

The Liberal government bought the Trans Mountain pipeline, which links the provinces of Alberta and British Columbia, from the American energy giant Kinder Morgan for $2.7 billion.

Alberta holds the planet’s third-largest oil reserves. The goal was to speed up the export of oil from the province to new foreign markets. In exchange, the Canadian government promised to invest the profits in green technology.

Many Canadian environmentalists viewed Trudeau’s move as a betrayal. The deal may cost him crucial votes on Monday, with the prime minister currently polling neck-and-neck with Canadian Conservative party leader Andrew Scheer.

For activists, Trudeau, who was a symbol of hope when he took office in 2015, is no longer a change agent but the man who didn’t do enough for the environment.

On university campuses, protesting for the environment – one of the key issues in the election – is all the rage.

“We’re seeing an uptick in membership in all sorts of environmental groups at McGill” in recent weeks, said Audrey Nelles from Divest McGill, a student group advocating for the prestigious Montreal university to withdraw funds it has invested in fossil fuels.

“I think that after the Harper years, there was a lot of hope,” said Annabelle Couture-Guay, also of Divest McGill, referring to Trudeau’s Conservative predecessor Stephen Harper.

But “buying the Trans Mountain pipeline, that was a huge disappointment. It made a lot of people cynical,” she said.

The pipeline issue has also provided Trudeau’s rivals with plenty of ammunition.

The Liberals “tried to please everyone, and that drew criticism from the right for not having gone far enough in economic development, and from the left for having bought the pipeline,” said Daniel Beland, a political specialist at McGill.

At the end of September, the New Democratic Party – whose leader Jagmeet Singh has risen in the polls and appeals to the Liberal left-wing – issued a five-word statement responding to Trudeau’s climate plan: “You. Bought. A. Pipeline.”

Liberals have pledged net-zero carbon emissions by 2050, two billion trees planted and the promotion of clean technology.

There have also been a few advances, such as a federal carbon tax plan, the protection of 14 per cent of marine and coastal areas, and the publication of major scientific reports on climate change in Canada.

Young voters demanding stronger climate policy are facing a dilemma because of Canada’s first-past-the-post system: voting for smaller parties can split the vote between the left and the centre, opening the door for the Conservatives.

But protesters at “Fridays for Future”, a movement started by teenage Swedish activist Greta Thunberg, promise to continue applying pressure – whether or not they are of voting age.

Thunberg herself was in Alberta over the weekend to rally against domestic oil production as its premiere inaugurated a new pipeline the very same day.

“We are doing this because our future is at stake,” Thunberg told a crowd that organisers estimated to be in the thousands, which gathered in front of the provincial legislature in Edmonton.

“We would like to have a future too.”