The NSW Greens have backed calls for an independent party to scrutinise James Packer's proposal for a $1 billion development at Barangaroo but say the state's chief auditor is not the man for the job.

The government has already commissioned and received a Deloitte report into Mr Packer's Crown Limited proposal, including whether a casino is necessary for its financial viability.

But the government says the report is cabinet-in-confidence and will not be released.

Greens MP John Kaye on Tuesday told AAP he would move to force the government to release the Deloitte report when parliament resumes.

"There is an urgent need to open this process up and put not just another set of eyes on the proposal but 7.2 million sets," he said.

Dr Kaye said an independent assessment panel announced by the government last week and chaired by former Future Fund chairman David Murray would work "behind closed doors".

The government has promised the panel's findings will be made public.

Fairfax Media on Tuesday reported independent state MP for Sydney, Alex Greenwich, had written to NSW Auditor-General Peter Achterstraat asking that he work with the Murray independent assessment panel.

"It is essential that the panel is assisted by an organisation with experience in financial assessment and whose sole aim is to maximise public benefit," Mr Greenwich reportedly wrote.

The auditor-general's usual role is to examine and assess projects after they have been completed.

Dr Kaye said involving Mr Achterstraat at this stage would compromise his office's independence.

"Mr Greenwich's proposal comes from a good place," he said.

"However it would have unintended consequences that could undermine the ability of the auditor-general to review the casino assessment once it is completed ... There is an urgent need to open this process up."