Former Australian Democrats leader Andrew Bartlett is poised to return to federal parliament as the Greens' replacement for Queensland senator Larissa Waters.
Mr Bartlett, who convenes the Queensland Greens, was second on the party's ticket at last year's federal election and is in the box seat to snare the senate spot after his colleague's Canadian citizenship blunder.
Mr Bartlett says he, like all party members, is devastated by Senator Waters' resignation.
"Larissa has been a great servant for the state of Queensland and a strong, effective advocate for the policies and values which the Greens stand for," he said in a statement.
"My immediate focus is on working with the many thousands of wonderful members and supporters of the Greens in Queensland to work through this situation so that we can continue to present an effective alternative to the establishment parties who fail our community and our environment so badly."
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He said party members would be having many conversations in coming days to determine the best way forward.
Mr Bartlett spent nearly 11 years in parliament for the Australian Democrats from 1997 until 2008, two of them as party leader.
His leadership was marred by an incident late in 2003 when he drunkenly manhandled Liberal senator Jeannie Ferris on the floor of parliament in an argument over several bottles of wine he took from a Liberals Christmas party.
He later vowed to abstain from alcohol.
He lost his Senate spot at the 2007 federal election as the Democrats were wiped out, before drifting to the Greens in 2009.
Mr Bartlett stood for the Greens in the federal seat of Brisbane in 2010, before being put forward as their pick for Brisbane Lord Mayor in 2012 and senate candidate in 2016.
