Labor leader Bill Shorten last week hardened his previously non-committal stance on the mine when he said he was "increasingly sceptical" of the Adani project, casting doubt over the economic case in light of the world coal market struggling.
But Greens leader Richard Di Natale said voters would not accept "weasel words" from Labor.
"This has to be an absolute iron-clad commitment that the Labor party makes sure this mine doesn't get built," Senator Di Natale told reporters on Monday.
Shorten's comments came as Labor entered a tight by-election battle with the Greens for the Melbourne seat of Batman, with Adani shaping up as a key issue in an electorate about 2000km from the proposed mine site.
Labor's candidate for Batman, union leader Ged Kearney, told reporters last week she didn't think the Adani mine would go ahead.
Resources Minister Matt Canavan said this year's coal market started strongly, with the thermal coal price more than double last year's and the coking coal price doubling in the past two years.
"It's clear Mr Shorten knows nothing about coal mining," he said in Senate question time.
The protesters who gathered outside parliament said they were mobilising in 2018 with campaign boot camps to "fundamentally shift the politics of coal".
Joseph Zane Sikulu, Pacific Project Co-ordinator for 350.org, said the Stop Adani movement had also spread beyond Australia.
"We called Australia out for the fact that they are not a good big brother to the people in the Pacific," he said.
"Those realities are no longer just ours, they are yours as well," he said of rising sea waters and reef bleaching caused by climate change.
Adani chairman Gautam Adani told a forum in New Delhi on Friday that resistance to the project in the Galilee Basin had been intense.
"In recent years our project has faced intense resistance abetted by some international NGOs and competitors who have turned to vicious personal attacks and used the press to their advantage," Mr Adani said, according to Indian business news website Livemint.
Adani has said the $16.5 billion mine would bring 10,000 jobs to the region.
Mr Canavan was asked about reports Adani falsified samples when appealing a fine for a spill from Abbott Point in 2017 during Cyclone Debbie, but he said it was a state matter.
Adani has strongly denied the reports.