New Zealand prime minister Jacinda Ardern’s self-imposed neutrality in last year’s cannabis referendum could have been the decisive factor in the Cannabis Legalisation and Control Bill’s narrow defeat, according to researchers.

Ardern chose not to reveal her voting preference during the campaign so she would be able to implement the result from a position of neutrality. It was only after polls closed that she confirmed she had voted Yes in both the euthanasia and cannabis referenda.

Efforts to legalise cannabis failed, with 48.4% of voters in favour and 50.7% against.

Jacinda Ardern: kept her voting intentions secret until polls closed.

The team at Massey University said another factor was that the referendum format created a public campaigning environment that encouraged persuasion and selective use of evidence rather than rational discussion of all the evidence and related knowledge gaps.

The researchers said both sides were guilty of selectively presenting information that might benefit their cause, with No campaigners exaggerating the impact of cannabis on road accidents and workplace safety and Yes campaigners promoting Ardern’s support for non-criminal responses to cannabis use but ignoring her concerns over youth access.

They added it did not appear to be the case that No campaign groups outspent Yes campaigners online, and the leading digital media appeared largely neutral or mildly in favour of reform.

Voting patterns followed traditional conservative-liberal, urban-rural and age divides, with strong support for cannabis legalisation in major cities and among young people.

The authors concluded: “The recent New Zealand experience illustrates the uncertainties of attempting to achieve cannabis law reform via a public referendum vote.”

The research paper, labelled as opinion, was published in the Drug and Alcohol Review.

Prior to launching Cannabiz, Martin was co-founder and CEO of Asia-Pac’s leading B2B media and marketing information brand Mumbrella, overseeing its sale to Diversified Communications in 2017. A journalist...