[2] Peter Fraser is the longest-serving Labour prime minister, serving 9 years, 261 days between 1940 and 1949.

A new leader is elected whenever a vacancy arises, whether due to resignation, incapacitation, or following a motion of no confidence by the parliamentary caucus.

If one cannot be found then the leadership is determined by an electoral college comprising the caucus (40% of the total vote), party members (40%) and affiliated trade unions (20%).

If they fail to receive endorsement then the position of party leader is vacated and an election is triggered.

[6] Unique to Labour, the party's caucus possesses the right to elect MPs to Cabinet, rather than the leader choosing them.