Britain votes tomorrow on change to its voting system, just two days after the news today from Canada demonstrated, as graphically as anything could, why change is necessary. But the insularity and intellectual poverty of the referendum debate is such that the lesson is unlikely to be heeded.

Stephen Harper, Canada’s Conservative prime minister in a minority government for the past two terms, finally won a majority in Monday’s general election — 167 seats out of 308. But it came courtesy of the electoral system, not the voters.

Harper’s Tories won with only 39.6% of the votes. Against them, the three centre-left parties of New Democrats (30.6%, 102 seats), Liberals (18.9%, 34 seats) and Greens (3.9%, one seat) had a clear majority between them. As I said last time Canada voted, two and a half years ago, the voters wanted “a centre-left government. But they’re not going to get one.”

That’s first-past-the-post voting for you — the same system used in Britain. Thursday’s referendum would replace it with an optional preferential system like that used in New South Wales and Queensland (in Britain it’s called the “alternative vote”, or AV). All the indications are that it’s going to go down, and even if it should happen to get up it won’t make a lot of difference to British politics. But it would be some sort of protection against an outcome like Canada’s.

For make no mistake, this result is an absolute travesty. The most obvious parallel is 2005 in Britain, when Labour under Tony Blair won a clear majority with less than 36% of the vote. But then at least Blair could could claim that the majority of the electorate was anti-Tory. This time, Canada has ended up with a government that on anyone’s story is dead against the will of the electorate.

If democracy means anything, it means that things such as this shouldn’t happen.

Preferential voting is no panacea; it can produce strange results too, as in South Australia last year when Labor held office despite being clearly outvoted on a two-party-preferred basis. But it would offer safeguards against a Canada-style result; an exchange of preferences between Liberals and New Democrats might not have given them a majority, but it would at least have produced a hung parliament, like the last one.

If the “Yes to AV” campaign in Britain was on the job they would be deluging the country pointing out this obvious injustice. But there’s no sign of that happening, and so few people understand the basics of electoral systems that it is very hard to make the case for change. You have to start by explaining things that most voters are reluctant to admit they don’t know in the first place, and ignorance provides fertile ground for a scare campaign against change.

Australia has had stable government for 80 years with preferential voting, but (despite the valiant efforts of Antony Green “Australia” is still being used as a bogey word by the “No” campaign. There’s equally little chance of Canada’s experience being given its due weight.

Harper now has the mandate that he wanted. But his adventurism in government may be tempered by the knowledge that should his opponents combine — even to the extend of an agreement to avoid three- or four-cornered contests in critical seats — his party would be in deep trouble.

The lesson is all the more obvious because that’s exactly where the Conservatives come from. In the 1990s, the Liberals scored decisive victories because their opposition was divided between the Reform Party, strong in Canada’s west, and the Progressive Conservatives, strong in the Atlantic provinces. The union of the two to form the Conservative Party was the essential precondition to Harper’s success.

Failing a change to a more democratic electoral system — unlikely even in Britain, and not on the agenda in Canada — the centre-left will have to learn to co-operate if its electoral support is to translate into a parliamentary majority.