BC Green Party Leader Andrew Weaver is threatening to bring down the province's six-month-old minority NDP government if Premier John Horgan courts potential investors for a liquefied natural gas industry during his upcoming trade mission to Asia.

The Greens agreed to a formal alliance with the NDP last July, allowing Mr. Horgan to take power after 16 years of Liberal government. But on the eve of Mr. Horgan's tour, which includes meetings with the backers of a proposed LNG facility for the B.C. coast, Mr. Weaver is warning that he is willing to walk away from the pact.

"If BCNDP caucus continue the generational sellout embodied in the LNG folly of the BC Liberals, their government will fall," he tweeted in response to a Globe and Mail story on the conflict between LNG and climate action.

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Mr. Weaver did not respond to interview requests on Thursday. However, in a social-media exchange, he explained that his party signed the confidence-and-supply agreement (CASA) with the NDP because both parties had agreed to tackle climate change by reducing greenhouse-gas emissions – a goal that would be challenged by the significant GHG output associated with the production of LNG.

"The reason why we agreed to the CASA agreement with the NDP is their supposed commitment to GHG reduction. A push for #LNG means they are not serious," he wrote in one tweet. "We are willing to let BC voters have their say. We would have been deceived."

In a subsequent tweet, he reiterated that the NDP government would fall on a no-confidence motion if it sought to secure a new LNG industry. The Greens rejected an alliance with the pro-LNG Liberals last June, but the two parties combined have enough seats to defeat the NDP minority on a confidence vote when the legislative session resumes in February.

B.C. Environment Minister George Heyman said on Thursday he hopes to talk to Mr. Weaver about how the province can tackle GHG reductions while still pursuing LNG.

"The Premier is talking to people about LNG development. He has always been clear that our government is interested in that," he said in an interview. He added that his ministry, responsible for climate action, is still working on its own models to measure the GHG footprint of LNG facilities.

"What Andrew Weaver and I should discuss is what our government's overall climate action plan looks like and what our proposals are that we are developing to reduce emissions across industry, across transportation and across buildings and homes."

In December, the province quietly updated its emissions inventory, showing that as of 2015 – the most recent year available – B.C. has veered far off its 2020 reduction targets. Instead of approaching a reduction from 2007 levels of a third, the province had reduced emissions only by about 2 per cent.

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The climate targets were set by Liberal premier Gordon Campbell in 2008, when the B.C. carbon tax was imposed. But the tax was frozen in 2013 under Mr. Campbell's successor, Christy Clark, and emissions started climbing again.

"The important thing for all of us to remember – including the Green Party – is that we are in this mess because under Christy Clark emissions went up," Mr. Heyman said. "The case I would make to Mr. Weaver is 'Let's work together on an overall plan that would bring emissions down.'"

Mr. Heyman is a former executive director of the Sierra Club BC, one of the environmental organizations leading the charge against LNG.

"If LNG Canada goes ahead, it alone could account for more than three-quarters of B.C.'s allowable emissions in 2050," Sierra Club BC climate campaigner Jens Wieting said in a news release on Thursday. "No matter what government is in power, exporting liquefied fracked gas to Asia will make it impossible for B.C. to meet our legislated climate targets; the math simply doesn't add up."

This week, Mr. Horgan told reporters that his message to potential investors will include a reminder that any projects need to fit within his government's climate action plans.

However, his government has signalled it is interested in bringing the massive investment potential of LNG to B.C.

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Briefing notes prepared for cabinet when an LNG proposal by Malaysia's Petronas stalled last summer included this message for the public: "Our government is committed to working with the LNG industry to ensure we are competitive."