Lawmakers in the Nationals party elected Michael McCormack as their leader. The junior coalition partner's former leader Barnaby Joyce resigned Friday as both party leader and a Cabinet minister, AP reported.
Joyce did not resign from Parliament, ensuring that Prime Minister Malcolm Turnbull's single-seat majority in the House of Representatives is maintained.
McCormack is a former veteran’s affairs minister. The rural-focused Nationals' leader automatically becomes Turnbull's deputy under their coalition agreement with the prime minister's conservative Liberal Party.
"I want to make sure that people know that in me they will have a fighter. I have a huge challenge ahead of me," McCormack, 53, told reporters after his election.
He was later sworn in as deputy prime minister as well as minister for infrastructure and transport, portfolios that Joyce had held.
Recent controversies over Joyce's private life had strained the coalition partnership.
Joyce is estranged from his wife of 24 years and four daughters and is expecting a baby in April with a former press secretary.
While Joyce argues that his personal life is private, there have been questions raised about two government jobs his current partner Vikki Campion got after she left his office and the rent-free accommodation they share in an apartment owned by a wealth political donor.
Joyce said reports that a woman had made a sexual harassment complaint against him was the "straw that breaks the camel's back." He denied the allegations, and said he requested they be referred to police for investigation.
Joyce and Turnbull have openly attacked each other in recent weeks.
Turnbull accused his deputy of making a "shocking error of judgment" by having an office affair. Joyce described his leader's remarks as "inept" and "completely unnecessary."