The Prime Minister is usually the leader of the majority party (or coalition of parties) in the House of Representatives. He has achieved his position as leader through a vote of the parliamentary representatives of his party, often as a result of challenging the previous leader.

Sometimes a prime minister loses his position through such a challenge. The most recent example was when Bob Hawke was beaten in a party room vote by Paul Keating, who then became the new Prime Minister.

Sometimes the Prime Minister is a leader of a minority party, and could potentially be outvoted in Parliament by the representatives of the other parties. This usually only happens with the approval of the Governor-General. sometimes it works, sometimes it doesn't. when it doesn't, the Governor-General appoints a different leader or calls an election. We had one Parliament where there were three parties, each with roughly equal numbers, and all three leaders had a go at forming a government.