Queensland unionists and activist groups believe there has been a "cover-up" of black lung cases, claiming the number could be as high as 1000.
The accusations came as a Senate inquiry into the recurrence of the disease prepares to hold public hearings in Brisbane on Monday.
The CFMEU said there had been clear failings, particularly by the Queensland government, to ensure coal dust is safely managed at mine sites.
It said no-one had been properly checking to ensure mines are minimising workers' exposure to dust, and accused the government of presiding over a failed health-monitoring system.
About 150,000 screening X-rays held by Queensland's mines department haven't been processed, and radiologists tasked with checking them aren't qualified to properly detect black lung, the union claimed.
"It's been hidden, covered up," CFMEU safety and health officer Jason Hill told the ABC.
In its submission to the inquiry, the union said the recurrence of black lung, caused by the long-term inhalation of coal dust, has exposed a litany of failings.
In January this year, Natural Resources and Mines Minister Anthony Lynham pointed to a five-point plan to combat risks of black lung.
That included a major review of the Coal Mine Workers' Health Scheme.
After three initial cases were reported last year, an audit carried out on the state's 12 underground coal mines found one was exceeding coal dust levels.
In January, a 51-year-old electrician who had worked in underground mines became the state's sixth case of black lung disease.
Eight mines over the past 12 months have been directed to either improve monitoring or bring respirable dust levels back into compliance, the Department of Natural Resources and Mines said.
"All coal mines in Queensland are currently in compliance with regulated dust management standards," a spokesman said.
The department rejected claims that there were 150,000 X-rays waiting to be processed.
"Medical assessments, including chest X-rays performed under the health scheme are provided by the medical professionals involved directly to the coal worker concerned," the spokesman said.
"Medical assessment records held by the department are those that have already been completed and reviewed by medical professionals and returned to the patient."
The Queensland Resources Council dismissed claims of 1000 black lung cases as being without foundation, and amounting to "irresponsible scaremongering".
But lobby group Stop Brisbane Coal Trains, which wants a royal commission, said the affair amounted to "Queensland's Watergate".
"It reeks of ongoing and deliberate deception," spokesperson John Gordon said.
