Environment Minister Robyn Parker and the state's environmental watchdog have been accused of misleading Parliament and the public in a ''systematic cover-up'' of information about whether uncovered coal trains are polluting the air in Newcastle and the Hunter Valley.
The Hunter Community Environment Centre has obtained thousands of pages of documents it says show Ms Parker and the Environment Protection Authority gave public assurances that no elevated levels of coal dust were detected from the trains even after findings from government experts that there was a strong relationship between the coal trains and a spike in air dust particles.
It says the documents show the methodology used in reports by the coal train operator, Australian Rail Track Corporation, to monitor pollution was flawed.
HCEC spokesman James Whelan says the documents show the EPA prepared a draft press statement saying coal trains did not increase pollution before the agency received the monitoring results.
''There has been a systematic cover-up that warrants a parliamentary inquiry,'' Dr Whelan said.
''The documents demonstrate a public relations effort of deception and spin to conceal the extent and nature of pollution caused by uncovered trains.''
Opposition environment spokesman Luke Foley said the EPA, seemed to be focused on protecting polluting industries rather than looking after community health.
''If the minister has unknowingly misled the Parliament as a result of false advice from the EPA, she must correct the record immediately,'' Mr Foley said. ''And she needs to put a broom through the EPA.''
Ms Parker has denied making misleading statements, saying all statements were made on the latest advice of her departments.
EPA chief executive Barry Buffier says he stands by all EPA statements and is keeping an open mind on covering coal wagons until there is further evidence. A review of all data by an independent expert, Professor Louise Ryan of UTS, is due this month.
The trouble has centred on coal trains that haul uncovered coal from Hunter Valley mines to Newcastle port and are licensed for pollution by the federally owned Australian Rail Track Corporation. Residents concerned about the health impacts of coal dust launched a statewide campaign to cover the wagons.
The ARTC had been required by the EPA to monitor and report on pollution twice in 2012. When its report was released last year, it said there was no appreciable difference between the dust levels from the movement of loaded coal trains and other types of freight train. But an earlier version of the report was then leaked to the HCEC that showed it had been doctored, and the conclusions had been reversed.
The revelations prompted 500 residents to call for an inquiry and the HCEC used freedom of information laws to obtain the internal EPA documents. They show technical reviews of the ARTC reports by the experts from the Office of Environment and Heritage had found a significant spike in pollution as coal trains passed.
The documents reveal that the EPA knew in September 2012 that the ARTC report contained errors and missing data and had ''too much averaging to be of immediate use''.
Emails showed EPA staff believed ''we have jumped the gun'' by drafting pollution reduction programs before analysis of the report. They reveal internal EPA concerns that major errors with the methodology and analysis would be noticed when the report was released.
The document trail shows the EPA had prepared a media statement before seeing the results of the study. The statement had attributed assurances that there were no health concerns about particulates from train movements to Professor Wayne Smith of NSW Health, before the Health Department had received the report or considered its response.
The EPA staff member who drafted the comments anticipated that NSW Health would be uncomfortable about it, but said he could see ''no harm in trying it on them''.
An EPA spokeswoman said the statements attributed to NSW Health been the subject of interdepartmental discussions but the EPA then decided not to use them.
Mr Buffier said the documents showed rigorous discussion. He said: ''No one piece of correspondence can be viewed in isolation of the entire conversation.''