Labor wants to pass a bill this month to legislate a state 2050 net-zero emissions target and an independent commission to review and report annually on the government's progress.
The government bill would also enshrine a 2030 goal of a minimum 50 per cent cut in greenhouse gas emissions on 2005 levels.
But those targets mimic unlegislated targets set by the previous coalition government that were "too little, too late", Greens MP Sue Higginson said.
She said her seven-member party room and five other crossbenchers were unable to pass the bill in its current form.
"We need right now - more than ever before - ambition, courage and leadership," Ms Higginson said on Friday.
"We know communities are struggling now under climate change - the cost of climate change and inaction is exorbitant."
Year 10 student Min Park said younger generations would bear the brunt of lacklustre reforms.
The group points out official state projections show the state is already on track to cut emissions by 55 per cent by 2030.
Ms Higginson would not be drawn on a 2030 target that would be palpable to the cross bench, saying the ball was firmly in the government's court.
"They need to come back with more ambition."
Independent Alex Greenwich pointed to the thousands of school students taking to the streets across the nation on Friday to protest the speed of climate action.
"This is the generation we should be legislating for ... and that means this legislation needs to be bolder, stronger and more ambitious," he said.
Year 10 student Min Park warned lacklustre reform would disenfranchise younger generations.
"How dare you make us responsible for this climate crisis," she said.
Thousands of students have taken to the streets to call for more climate action.
NSW Environment Minister Penny Sharpe has previously described each target as "a floor, not a ceiling" and said the government would keep the 70 per cent target for 2035 set by the previous coalition government.
"The whole point of legislating the targets and having the Net Zero Commission is it'll track how we're doing and, if we need, to make sure that we get there," she told reporters in October.
The issue will come to a head in the coming fortnight in state parliament, where the government needs two crossbenchers in the lower house and six in the upper house to pass legislation opposed by the coalition.
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