Open this photo in gallery B.C. NDP Leader John Horgan and B.C. Green Party Leader Andrew Weaver shake hands after signing an agreement on creating a minority government in 2017. CHAD HIPOLITO/The Canadian Press

Over the past year, B.C.’s Green Party has voted in lockstep with the NDP on every piece of legislation that has come into effect: 50 bills over two sessions, touching on matters ranging from vehicle insurance to lobbying reform. Despite Green Party Leader Andrew Weaver’s occasional criticism of his governing partner, no Green MLA has ever voted against an NDP bill.

That record reflects the pact reached last year between the Green Party and the NDP that allowed the NDP to be sworn into government.

But the agreement could face its toughest challenge yet in the coming months when differences between the two parties over liquefied natural gas (LNG) come into sharper focus. Those differences will be an opportunity for the Greens to demonstrate their clout and their independence as part of the governing arrangement that Mr. Weaver resolutely declared last year was not a coalition.

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“LNG will be a test,” said Michael Prince, a professor of social policy at the University of Victoria. “It will be up to the Greens to say how does that figure into the overall scheme of things in terms of what else is being proposed,” he added.

When the results were counted in the May, 2017 election, the Liberals held 44 seats, the NDP 41 and the Greens three. The agreement between now-Premier John Horgan and Mr. Weaver allowed the two parties to topple the Liberals in a non-confidence motion after 16 years in power.

The eight-page confidence-and-supply agreement calls on the Greens to support the NDP on votes where the confidence of government is tested, primarily on budget matters. In exchange, the Greens are to be consulted on policy. The pact also included policies that were a condition of Green support, including proportional representation and lobbying reform.

Differences on LNG have been one of the most contentious issues in the relationship.

On his Twitter account on Jan. 17, 2018, Mr. Weaver said the “NDP government will fall in non-confidence if after all that has happened it continues to pursue LNG folly.”

He subsequently softened his position, saying he would give the NDP until the fall to say how it would balance tax concessions and other measures to attract LNG investment with efforts to reduce greenhouse gases.

In recent weeks, there has been speculation that LNG Canada – a $40-billion LNG project led by Royal Dutch Shell PLC – will soon announce a final investment decision for its proposed facility in Kitimat. If the decision is to proceed, the once-theoretical LNG sector starts to take shape and with it, the need for a regulatory framework.

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Shipping LNG to Asian export markets was a cornerstone of the former Liberal government’s economic plans; in 2013, former premier Christy Clark forecast three plants would be up and running by 2020. To date, none have been built.

In its 2017 campaign platform, the NDP said LNG could still represent a “significant opportunity” for B.C. and set four conditions for any project to go ahead.

But the Green platform called for reduced reliance on LNG development, saying “new investments for export are inconsistent with our commitment to move toward a low-carbon future.”

In March, Premier Horgan announced a new regulatory framework for LNG, including tax breaks. Those concessions – and buzz around LNG Canada – have put pressure on the year-old partnership.

“LNG is a sticking point,” says Sonia Furstenau, Green Party MLA for Cowichan Valley. “We have indicated that we don’t support their [NDP] proposed tax break regime for LNG. We don’t think that increasing subsidies for the fossil fuel industry is the direction that any government should be going right now,” she added.

The two parties are talking about possible solutions to the LNG standoff, Ms. Furstenau said.

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Citing advice from Helen Clark – the former prime minister of New Zealand who spoke in favour of proportional representation at an event in Vancouver in June – Ms. Furstenau said Green support reflects behind-the-scenes negotiations.

On some fronts, it appears that the Green Party has given ground. Before the election, the party opposed Site C, a massive hydroelectric project now under construction in Northeast B.C. In the confidence-and-supply agreement, the parties agreed to refer Site C to the B.C. Utilities Commission for review. The commission’s findings were inconclusive. But with $2-billion of work already completed on the project, there was an economic argument that the dam was too far along to stop and Mr. Horgan, in December, 2017, said the project would go ahead.

The Greens also campaigned on raising the property-transfer tax for foreign buyers – introduced by the Liberals in 2016 at 15 per cent - to 30 per cent and applying it across the province. In February’s budget, the minority NDP government raised the tax to 20 per cent and expanded it from Metro Vancouver to some, but not all, parts of the province.

Liberal leader Andrew Wilkinson maintains the Green Party has had little influence. “They will have a chance this fall to show their true colours,” Mr. Wilkinson says. “Are they prepared to support the NDP or not? Because the pattern so far is that they make a lot of noise and then cave into the NDP every time.”

The Green Party maintains it has had significant influence, including amendments to the elections financing act and new legislation on lobbying reform, which was mentioned in the Green Party platform, but not the NDP’s.

Some pundits expect the Green Party to put proportional representation ahead of other priorities. That electoral reform issue is headed to a fall referendum. The NDP has proposed three proportional representation models to replace the first-past-the-post system. Voters in two prior referendums, in 2005 and 2009, did not back proportional representation.

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“If the referendum fails, as I expect it to, then I think all bets are off and the Greens may make more of an issue on LNG,” says Hamish Telford, an associate professor of political science at the University of the Fraser Valley.

“But if the referendum is successful and we move toward a system of proportional representation, then I think that becomes more important to the Greens than anything else and they will continue to back the government until the next election.”

He thinks the Green Party gave up some of its potential leverage by signing a four-year agreement. “They negotiated away all their bargaining power,” Mr. Telford says.

Ms. Furstenau disagrees. “The pressure exists, which is – you still need our votes. Ultimately, we still have to stand up.”