A NSW upper house inquiry has opposed approval of a giant waste-to-energy incinerator planned for Sydney's west, agreeing that community engagement by its proponent did not come within "a bull's roar" of best practice.

The $700 million Next Generation project proposed by Dial-A-Dump Industries at a site at Eastern Creek is seeking to burn as much as 1.105 million tonnes of waste a year.

The firm's amended plan attracted 949 public submissions against the project and just two in favour, the inquiry's report, Energy From Waste Technology, noted.

Dial-A-Dump Industries applied for approval of its $700 million waste-to-energy facility at the Eastern Creek industrial estate.

The inquiry noted doubts by the NSW Environment Protection Authority of the "thoroughness and veracity" of the human risk assessment.