One leading group says debate on the bill must be used to signal an end to the "climate wars" which have caused investors to "flee" the local market in recent years.

The intervention from the major investors comes as the Greens continue to resist Labor's proposal, despite the government agreeing to some minor concessions.

Labor's refusal to block future coal and gas projects remains the major stumbling block for the Greens, which have the numbers to kill off the government's legislation in the Senate.

The Peter Dutton-led Coalition remains opposed to legislated targets.

Climate Change and Energy Minister Chris Bowen will on Wednesday introduce the highly anticipated legislation, which would seek to enshrine Labor's 43 per cent 2030 emissions reduction target in law.

The government hopes to pass the bill through the lower house before the end of next week, with a Senate inquiry likely to be held before a vote in the upper house, possibly as soon as September.

Mr Bowen said legislating the targets would send a message to the world that Australia was "open for business" when it comes to investment in clean energy technology, as he warned a failure to pass the bill could tarnish the country's international reputation.

Former ACT deputy chief minister Simon Corbell is chief executive of the Clean Energy Investor Group, which represents 19 investors owning 70 projects worth a combined $24 billion.

Mr Corbell said there had been a "seismic shift" in sentiment among investors since the election of the Albanese government, which has far more ambitious climate goals than its Coalition predecessors.

But Mr Corbell warned Australia would continue to be viewed as a more "risky market" compared to other countries if Labor's targets weren't legislated.

He said investors could choose to favour more "stable" markets over Australia as a result.

"If there was a decision to not enshrine the target in legislation, that would stand in contrast to the environment in other markets," he said.

"It would mean there would be this shroud of uncertainty around how serious Australia's commitment was, and that would affect investor sentiment."

Highlighting the scale of investment needed to transition the national electricity market, Mr Corbell said his group's analysis estimated around $70 billion of new investment would be needed out to 2042.

Mr Corbell, a former ACT climate change minister, said parliament should "bank" Labor's reforms and then work towards more ambitious goals.

Investor Group on Climate Change policy director Erwin Jackson said the upcoming debate presented a chance to send a message to international investors that Australia's climate wars, and the policy uncertainty which has accompanied it, were ending.

"We have seen investors fleeing Australia to invest in countries with more stable policy measures to support things like clean energy," he said.

"Investors are human. If they stick their hand in a fire and it's burned they're not going to come back and that's what's been happening with the climate wars in Australia.

"[This legislation] is more about signaling an end to the climate wars than actually necessarily signaling the level of ambition itself."

Mr Bowen confirmed tweaks had been made to the draft legislation after talks with the Greens and crossbenchers, including clarification that targets can only be increased in the future and that the 43 per cent 2030 goal was a floor not a ceiling on the government's ambition.