The leader of the third force in Australian politics, Greens Sen. Bob Brown, has announced his resignation.
The 67-year-old announced Friday that he has resigned as Greens leader and will resign from the Senate in June after 16 years to "make room for renewal" in the party.
The left-wing Greens have enabled Prime Minister Julia Gillard's center-left Labor Party to form a minority government since 2012.
Political scientist Nick Economou says he does not expect Brown's departure to weaken Gillard's tenuous grip on power.
New leader Christine Milne says the party's agreement to support the government remains unchanged.