The 2018 provincial referendum on electoral reform will be the last word on whether voters want to change how they select their elected officials in British Columbia, Attorney-General David Eby said Monday.

Mr. Eby will launch public consultations later this week to shape the referendum question, providing both experts and average British Columbians with the opportunity to design what the question – or questions – will be, and to shape rules on spending limits and any public funding for proponents.

"The goal is to provide British Columbians with a very clear opportunity to state their preference about where they want to go," Mr. Eby said in an interview. "I just have a hard time imagining, coming out of a process like that, that there could be any further discussion to be had."

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British Columbians have already been asked twice in the past 12 years if they want to change the existing first-past-the-post voting system, and Mr. Eby says, if the measure fails again, "that would settle the question."

The NDP minority government, in its agreement with the BC Green caucus, has promised a mail-in ballot next year that will ask if voters want to change to some form of proportional representation – a voting system where the number of seats each party gets in the legislature is based on their percentage of the popular vote.

For the Greens, working toward proportional representation is a fundamental tenet, and at a recent roundtable forum with The Globe and Mail, party leader Andrew Weaver said that commitment won't disappear even if voters reject change for a third time. "It defines who we are," he said.

However, Mr. Weaver said there will be little public appetite to keep going back to voters, should this vote fail to yield a change to the voting system. "I don't think people would want you to … have a referendum every four years – so it's not the last one in the future, but certainly I would say for the foreseeable future."

In 2005, B.C. voters were asked if they wanted to replace the current first-past-the-post system with one that would use a single transferable vote (STV). That proposal won 57.7-per-cent approval from voters, just below the 60-per-cent threshold that had been set as the minimum level of required support.

In 2009, voters were asked again to approve a shift to the STV system, but support dropped to just below 40 per cent.

The STV system – a form of proportional representation that allows voters in each riding to rank candidates by preference – had been proposed by a citizens' assembly that had been appointed to study electoral reform. Mr. Weaver said the vote failed because it was too difficult to explain how the new voting system would work.

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But now, with both the NDP and Greens campaigning for change, Mr. Weaver says he is hopeful that this time around voters will embrace a new voting system. The Greens have agreed to support the NDP government on key measures, in part as a demonstration to show how a minority government system can work in British Columbia.

In last spring's provincial election, the Liberals and NDP each earned slightly more than 40 per cent of the popular vote, but the New Democrats eventually formed a minority government with the support of the Greens, who received almost 17 per cent of the popular vote but took just three of 87 seats.

B.C.'s first-past-the-post system has delivered results in the legislature that can vary significantly from voters' preferences. In 1996, the NDP formed a majority government even though the Liberals had a greater share of the popular vote. (The NDP won more seats, while the Liberals' votes were spread out.) In 2001, the Liberals captured 77 of 79 seats in the Legislature with just 57 per cent of the total votes cast.

Premier John Horgan has said he will actively campaign in favour of change, arguing that the current system is unfair.

The referendum, to be held as a mail-in vote in the fall of 2018, may offer more than one choice for a new model. If the measure passes with a bare majority of votes, British Columbia will use the new voting system in the next provincial election in 2021.

The opposition BC Liberals oppose the proposed law that will enable the referendum. Andrew Wilkinson, the Liberal critic for the attorney-general, has said the process "really tears at the fabric of our democracy."