The protesters - including former Green Party co-leader Russel Norman, Forest & Bird chief executive Nicola Toki and actress Robyn Malcolm - made their way down Queen Street as part of the March for Nature.
The bill will see three ministers in charge of deciding on whether major infrastructure or development projects should go ahead.
"This is your government, these are your ministers. Responsibility for this environmental nightmare rests with you."
The former Green Party co-leader and Greenpeace executive director Russel Norman believes the bill will be bad for the environment.
"The vast majority of New Zealanders - nine out of 10 people, when you survey them - say they do not want development that causes more destruction of nature."
Norman told the crowd in Aotea Square that the bill was worth fighting against.
"We will stop them - just like we stopped the oil exploration companies. We disrupted them until they gave up."
The government would be on the wrong side of history if it ignored protesters, Norman said.
Protesters interviewed by RNZ said the bill was a "dumb" decision and would take New Zealand backwards.
"It feels like this government's taking us back to the 1950s. It's just dumb on so many levels," said another.
"It's just old, archaic, dinosaur economics. It's old thinking that got us into this problem that we're in right now," another protester told RNZ.
Pro-Palestinian protesters were also at the rally, with banners accusing the government of being complicit in genocide.
Public service job cuts 'deeply distressing'
Meanwhile, thousands of people congregated in Wellington to protest government cuts to public service jobs.
Protesters met at the Pukeahu National War Memorial for speeches before walking down to the waterfront.
Public Service Association spokesperson Fleur Fitzsimons told the crowd that everyone at the rally was sending a message of resistance, opposition and protest to the government.
She accused the coalition government of having an agenda against the public service, and said the union was seeing the destructive impact of government policies first hand.
"It is causing grief, anguish, stress, emotional collapse.
"It is deeply distressing to the workers who are losing their jobs. They are not only distressed for themselves, and their families, but they are deeply worried about what will happen to the important work they are doing on behalf of us all."
Other speakers included representatives from the Cancer Society, early childhood education, housing, the care and support sector, disability rights, queer and trans services, health, and the public servants.
They called on the government to reverse their public sector cuts, stop privatisation, and invest in 'collective wellbeing'.
Event organiser and director of ActionStation Kassie Hartendorp said the rally was "just the beginning" of public action against austerity cuts.
"People across Aotearoa are beginning to realise that the economic arguments that the National party and others fall back on might not actually stack up.
"The idea that moving collective wealth into the hands of a few and hoping it trickles down is becoming less and less convincing to everyday people - and the government's programme of austerity has driven this home."
