Canada's oil and gas sector -- one of the largest in the world -- is actively undermining efforts to slash greenhouse gas emissions, climate think tank InfluenceMap warned Thursday.

An analysis of the nation's six largest oil companies -- which comprise 67.8 percent of the sector's market value -- as well as the industry's main association, found that they have resisted policy changes to reduce emissions while pushing for expansion of oil and gas output, the group said in a report.

This is despite committing to reach net-zero emissions by 2050, and in contrast to calls by the UN Intergovernmental Panel on Climate Change and the policy-shaping International Energy Agency for the rapid phaseout of fossil fuels in order to limit warming to 1.5 degrees Celsius.

"Despite the industry's 'green' PR, the evidence of active campaigning against meaningful policy suggests an insincere commitment to climate action," InfluenceMap analyst Sofia Basheer said in a statement.

She cited, as examples, the sector's support for new offshore oil and gas projects, liquid natural gas (LNG) facilities, and pipelines to the United States.

Several of the companies also pushed back against an emissions cap proposed last year.

The industry promoted ideas that supported these positions, including that an increase in Canadian oil and gas exports could replace coal elsewhere, enabling overall emissions reductions.

More recently, in response to Russia's invasion of Ukraine, the industry claimed that Canadian oil and gas could replace "hostile sources of energy" from jurisdictions such as Russia.

Canada is the world's fourth largest oil producer.

Government data shows the oil and gas sector's emissions increased by 74 percent between 1990 and 2020, and represented more than a quarter of total national emissions with 179 megatonnes of carbon dioxide emitted in 2020.

Four of the companies reviewed in the report -- Cenovus Energy, Canadian Natural Resources Limited, Imperial Oil, and TC Energy -- demonstrated "negative climate policy engagement," InfluenceMap concluded.

Suncor Energy and Enbridge, meanwhile, were said to "appear to engage positively on some areas of the energy transition while opposing others."

Suncor's advocacy for renewable energy development in Alberta -- home to massive oil sands deposits -- and the rollout in British Columbia of electric vehicle charging infrastructure were cited as positive engagement.

The Canadian Association of Petroleum Producers, which represents upstream oil and gas companies, meanwhile, appeared to be "the most active and oppositional to climate policy progress," the report said.