The NSW government has been urged to install filtration systems in the WestConnex ventilation stacks to reduce the level of pollutants emitted from the road project's tunnels.
The state's upper house Public Accountability Committee recommended filtration systems be installed on all current and future motorway tunnels in its WestConnex report released on Monday.
"We want a filtration system put in that will be effective and is supported by scientific investigations," committee chair Reverend Fred Nile told reporters in Sydney.
"I am concerned that the proposed WestConnex unfiltered tunnel ventilation stacks do not meet best practice standards."
Filtration will reduce carcinogenic pollutants emitted from the tunnels from being breathed in by nearby residents, Rev Nile said.
The committee - on which government MPs were in the minority - was troubled that both the World Health Organization and NSW Health challenged the coalition's assertion that the project's tunnel ventilation was world's best practice.
Monday's report also revealed transparency was "unsatisfactory" and called on the government to immediately publish the $16.8 billion project's financial model.
"This (WestConnex) would be the worst example of a lack of transparency," Rev Nile said.
Concerns were raised about the recent sale of a majority stake of the road toll project to Transurban which the committee says will likely "exacerbate existing transparency and accountability concerns".
The committee made 27 recommendations including that the government hold public planning inquiries and publish strategic business cases for all future major infrastructure projects.
Liberal MP Peter Phelps in his dissenting statement called the inquiry "dreadful" and said it had been a "litany from anti-car Green extremists, whingeing Baby Boomers and NIMBY's and often people who are all three".
While he acknowledged some aspects of the project were deserving of legitimate criticism he argued no amount of information would have placated opponents.
Community group Coalition against WestConnex said the report should alarm residents because it revealed "shocking" evidence of unacceptable impacts and transparency failures.
