Adam Bandt has hailed a "greenslide" as the Greens recorded its best ever election result, winning two lower house seats and holding hopes for two more.
The Greens have won the inner Brisbane seat of Ryan, held Bandt's own seat of Melbourne and were ahead in the counts for the seats of Brisbane (held by the Liberal National party) and Griffith (Labor's Terri Butler).
The party also expects to increase its numbers in the Senate, with hopes of winning seats in New South Wales, Queensland and South Australia.
With uncertainty remaining over whether Labor could form government in its own right, Bandt said the Greens were "willing to talk" with Anthony Albanese.
Bandt said his party always believed a grassroots campaign on climate placed them in a strong position in Queensland, but they had largely been ignored by major parties and the media.
"The Greens are on track for our best result ever," Bandt said. "People have backed the Greens in record numbers and delivered a massive mandate for action on climate and inequality."
The Greens launched a huge door-knocking effort in Queensland in a bid to pick up inner-city seats in Brisbane, pushing on climate inaction in the face of the floods that have devastated the region.
The party's primary vote has increased nationally by 1.9% to 12.3%.
Bandt said the outcome was a result of voters flocking to the party for the first time because of its strong commitment to climate action, including a commitment to net zero by 2030, and its alternative economic policy.
The Greens attracted about 2m primary votes.
"On key questions, economic questions, cost-of-living questions, we've offered a real alternative," Bandt told reporters on Saturday evening.
The Greens candidate for Ryan, Elizabeth Watson-Brown, told the Guardian she was "still processing" the news of her victory.
"We are witnessing a tectonic shift in Australian politics ... and Queensland is leading the way," she said.
There was an 11.2% swing to the Greens in Ryan with 54.1% of the vote counted.
The Greens were also ahead in Griffith and leading in Brisbane, but with postal votes still to be counted the final result may not be known for some days.
There was an 11.9% swing to the Greens in Griffith, previously held by Labor with a margin of 2.9%. Greens candidate Max Chandler-Mather was leading with 35.6% of the primary vote, with almost 60% of votes counted.
The Greens took the seat of South Brisbane in the last state election, which is in the same area as Griffith, turfing the former deputy premier Jackie Trad out of parliament.
Chandler-Mather, to chants of "Max, Max, Max", told a crowd of Greens supporters the results were a "beacon of hope" for people across the nation that you "do not have to settle for the political status quo".
"Let's be very clear, we are only just getting started," he said. "Think about how far we've come and imagine were we can go over the next 10 to 15 years if we continue on this trajectory.
"The biggest asset that the political establishment has is low expectations. Well tonight, we raised those expectations."
There was also a 6.6% swing to the Greens in Brisbane. With almost 60% of the vote counted, Greens candidate Stephen Bates had 28.5% of primary votes, ahead of Labor and just behind sitting LNP member Trevor Evans.
Bandt, who also received a 2.9% swing in his seat, said the party was hopeful it would pick up Brisbane.
"We've run hard in those seats and we will find out soon enough what the results are," Bandt said.
The Greens also achieved swings in excess of 9% in some regional seats in other states. In the northern NSW seat of Richmond, Greens candidate Mandy Nolan was leading the primary vote at 29.4% with just shy of half of the vote counted.
In the inner Melbourne seat of Macnamara, Greens candidate Steph Hodgins-May had received a 7.2% swing and was trailing 31.4% to Labor's 32.5% with just over half of the vote counted.
If the party wins the three Senate seats it would bring their number in the upper house to 12 and put them on track to hold the balance of power.
"If we manage that we'll be the biggest third party in the Senate," Bandt said.
"We've just had three years of droughts and then fires and now floods and floods again. People can see that this is happening and it is unfolding, and I think increasingly what we are seeing is that that cuts across all voting situations, cuts across all demographics.
"In the coming days, if there is a minority parliament we will work towards delivering a stable, effective and progressive government for the country."
Greens senator Larissa Waters wiped away tears at a party in West End's Montague Hotel on Saturday evening, where candidates from Brisbane, Griffith and Ryan gathered.
Waters said she was "completely overwhelmed" by results coming through in Brisbane and nationally, and told supporters to "revel in the glory".
Waters said it was "looking good" that she would soon be joined in parliament by three lower house MPs and one senator from Queensland.
