Parties are virtually always in opposition when they start giving party members a vote for leader. This is particularly likely to happen after an especially disappointing election result.
Once a party in a particular country gives its members a vote for leader, other parties in the same country tend to follow suit.
Newer parties are more likely to adapt this model than parties that are more established.
All four major Canadian parties choose their leader via one member-one vote.
Irish Labour was the first party in Ireland to allow its members to vote for the leader, in 1989. The Greens are the only other Irish party to choose its leader via one member-one vote.
The British Labour and Conservative parties allow their MPs to select leadership candidates who are then voted on by the party as a whole. British Labour uses an electoral college composed of MPs, unions and party members, the Tories are one member-one vote.
Australia and New Zealand are currently alone among English-speaking Westminster countries in the major parties choosing the leader via the parliamentary party only.
New Zealand Labour is currently reviewing options for electing its parliamentary leader, but an initial discussion paper recommends that party members be given a say. A final decision will be made by the party’s AGM in November.