EDMONTON -- Federal New Democrats spurned the pleas of their Alberta brethren and signalled a desire to shift their party back to the left Sunday by agreeing to explore the merits of a manifesto that calls for more drastic action to combat climate change.

Adoption of the principles of the Leap Manifesto came just hours before delegates to the NDP's national convention voted to replace leader Tom Mulcair, who led the party to a disappointing third-place finish in last fall's election on a moderate, centrist platform.

The manifesto advocates a swift end to the use of fossil fuels, including a moratorium on new infrastructure projects such as pipelines that perpetuate reliance on the non-renewable resources that contribute to climate change.

Spearheaded by documentary filmmaker Avi Lewis and his wife, anti-capitalism activist and author Naomi Klein, it declares Canada's record on climate change thus far to be "a crime against humanity's future." And it calls for "energy democracy" in which communities collectively control future renewable energy sources, rather than "profit-gouging" corporations.

On Saturday, Alberta's NDP premier, Rachel Notley, pleaded with New Democrats to understand that thousands of families in her province depend on natural resources for their living, and need a pipeline and support for the oil and gas sector to maintain their quality of life -- even while working to improve the environment.

The resolution adopted Sunday was watered down somewhat in an apparent bid to soften the blow to the party in Alberta.

It recognizes the manifesto as "a high-level statement of principles that speaks to the aspirations, history and values of the party." But it also stipulates that specific policies advocated in the manifesto "can and should be debated and modified on their own merits and according to the needs of various communities and all parts of Canada."

Grassroots New Democrats are to debate the policies that will flow from the manifesto as part of the run-up to the party's next policy convention in 2018.

Lewis stressed on the floor of the convention Sunday that the manifesto is not designed to be inconsiderate of those who work in the oil and gas industry.

"We recognize the pain and wrenching anxiety of tens of thousands of families in this great province of Alberta who are hurting because Big Oil wanted their labour in the boom and then bailed on them in the bust, which is precisely why the Leap Manifesto calls for training and resources for fossil-fuel workers," he said.

"In fact, it insists that a transition to a clean-energy economy must be led by a democratic participation of the workers themselves."

But Gill McGowan, president of the Alberta Federation of Labour, spoke against the resolution. While he was reluctant to oppose it, he said the manifesto could be turned into a dangerous political symbol that could be used by opponents in the province.

"When I first read the Leap Manifesto, I was excited because it reflected a lot of the things that I've been thinking about in terms of policy and politics," he said. "However, in politics, sometimes things become symbols and not policy and I'm afraid that's what is happening with the Leap document."

Indeed, just moments after delegates passed the resolution, Wildrose Leader Brian Jean took to Twitter to mock Notley's inability to persuade her own party on the need for pipelines.

"Premier Notley fails to get 'social license' for pipelines -- from the .NDP," he tweeted. "Disappointing."

Among other things, the manifesto calls for: