LONGUEUIL, Que. -- The feud between federal New Democrats and Greens took a strange twist on Monday, as NDP Leader Jagmeet Singh announced environmentalist Eric Ferland will be his party's candidate for the Quebec riding of Longueuil-Saint-Hubert near Montreal.

Not only is Ferland a former leader of Quebec's Green Party, but the incumbent in the riding is former NDP MP Pierre Nantel who defected to the Greens.

The Greens and NDP have been locked in a fierce battle for third place in public-opinion polls as each seeks to attract progressive voters unhappy with the governing Liberals and worried about climate change. That battle has included several candidates jumping between the two parties.

Singh described Ferland's decision to turn New Democrat as evidence that his party's environmental plan "is the most complete," even as he sought to underscore what he described as the main differences between the NDP and the Greens.

"We believe in the importance of tackling the climate crisis. We know how important that is and we are going to do similar things," he said.

"But where we differ is we're not going to leave workers behind. Where we differ is we have a solid position on a woman's right to choose. With New Democrats, there's no question what you're getting. You know you're going to get candidates that all unequivocally support a woman's right to choose and will defend that and will also expand access to abortion services."

Ferland described the decision to run for the NDP as "obvious" given their plan for tackling climate change, which includes ending fossil-fuel subsidies, providing more incentives for the development of clean energy and expanding the price on carbon to include Canada's largest emitters.

"Basically for me the NDP had the best environmental plan," Ferland told reporters during Monday's campaign event. "They've got a really coherent plan. It fits perfectly. ... For me it was obvious to make the change to the NDP."

While New Democrats are clearly counting on Ferland's candidacy to bolster their environmental credentials, they are also hoping it will convince Quebecers -- many of whom are worried about climate change -- to support the party like they did in 2011, when voters handed the NDP under Jack Layton a majority of the province's seats.

The NDP has struggled in Quebec since that high-water mark and there have been questions over whether Quebecers, the majority of whom support the province's controversial ban on religious symbols, Bill 21, would vote for Singh.

Singh over the weekend promised the province new powers over immigration, the right to withdraw from federal programs with federal compensation, and an expansion of its French language laws.

He has also repeatedly refused to commit to joining any court challenges of Bill 21, which would prevent Singh himself from working as a teacher or a police officer in the province. As a Sikh, he wears a turban.