The Lock The Gate Alliance argues that more than 2.1 billion tonnes of carbon dioxide could be ignored by planning bodies if state parliament passes the coalition's controversial bill.

The draft legislation to prevent the imposition of conditions regulating overseas emissions is being examined by an upper house inquiry on Thursday.

The bill would also remove a specific requirement for authorities to consider "downstream" emissions when assessing mining projects.

Julie Lyford from Groundswell Gloucester, who gave evidence at the Sydney inquiry, is "absolutely white-hot angry" about the proposal.

"Our communities will not take this sitting down," Ms Lyford told reporters on Thursday.

The region was already facing terrible climate impacts with one life lost during recent bushfires and rivers running dry, she said.

Georgina Woods from the Lock The Gate Alliance hopes the state government "having been through this cataclysmic summer" will rethink the bill.

The alliance tabled evidence at Thursday's hearing that more than 2.1 billion tonnes of carbon dioxide could be ignored by planning authorities under the proposed change.

The figure is based on estimates from resource companies who are pursuing 12 coal and gas projects likely to be determined in the coming 18 months, Lock The Gate says.

But Liberal MP Shayne Mallard argued during the hearing that authorities would still be able to consider emissions when deciding mining applications, and if they were bad enough refuse consent.

"The issue here is not allowing conditions that can't be enforced in an overseas jurisdiction," he said.

NSW Minerals Council chief executive Stephen Galilee said they agreed the focus should be on impacts generated in NSW, and downstream emissions should be the responsibility of the country in which they're generated.

However, they hold some reservations about the bill in its current form, Mr Galilee told the hearing.

Public Health Association NSW, the state's peak health policy organisation, was among other opponents of the bill.

"This is a retrograde step that's out of balance with science and the expectation of the community," Public Health Association NSW president Patrick Harris told AAP.

"This government is ignoring the very real and present danger climate change poses to people's health by considering this legislation."

Mr Harris warned if global emissions continue to rise there will be an increase in climate change-related illnesses including respiratory conditions.

Planning Minister Rob Stokes introduced the Environmental Planning and Assessment Amendment (Territorial Limits) Bill to the NSW parliament in October.

It followed the Independent Planning Commission last year imposing overseas emissions conditions on its approval of a coal project near Singleton.

The commission in 2017 rejected another project at Rocky Hill with a judge subsequently stating the coalmine would increase global greenhouse gas emissions at a time when a "rapid and deep decrease" was required.

Australian Associated Press