According to a senior Defence official, "no amount" of money has been budgeted to compensate Red Zone residents whose land, homes and businesses have been been polluted by toxic per- and poly-fluoroalkyl, more commonly known as PFAS chemicals, leaking from Williamtown RAAF Base.

Coalition Against PFAS president Lindsay Clout, of Fullerton Cove, said Defence continued to "deny, deflect and distract", while residents continued to suffer.

Defence has budgeted $53.8 million in legal fees for six matters, including three PFAS class action claims brought by more than 1000 residents from Williamtown, Oakey, in Queensland, and Katherine, in the Northern Territory.

Defence official Steve Grezeskowiak revealed in a Senate estimates hearing nothing had been set aside to compensate residents.

"I'm not aware of a figure that may have been allocated," he said.

Pushed about continigencies for one of the largest class action lawsuits taken against the federal government, Mr Grezeskowiak said compensation was an "unquantifiable contingent liability".

The class action is expected to be heard in the Federal Court in August after mediation failed.

Mr Clout, one of about 750 households caught in a plume of toxic contamination from the Williamtown base, said it was clear the Morrison government wasn't serious about addressing the "mess" caused by Defence, preferring to "drag the matter all the way through a long and expensive trial".

"The only new money the government is budgeting to address PFAS contamination caused by firefighting foams at over 90 sites across Australia, is for lawyers to defend claims against it," he said.

"The truth is Defence has launched a four-year war of legal attrition against its own communities and continues to drag out and delay any negotiated settlement or legal process."

The federal Department of Health maintains there is no consistent evidence that PFAS causes "important" health effects.

In contrast, a recent US government report into the effects of the chemicals found they were even more toxic than previously thought and can cause immune dysfunction, hormonal interference and certain types of cancer in humans.

Mr Grezeskowiak told the senate committee last month that Defence budgeted $205 million for PFAS examination and management across 27 sites next financial year.

This includes paying the salaries of 40 public servants, estimated at $120,000 each annually, and 44 consultants.

Spending was predicted to halve to $101 million in 2020-21, $59 million in 2021-22 and $32 million in 2022-23.

"We've completed around half of the investigations that are ongoing...," he said.

"The other half will be completed over the next year or so. We're moving into producing PFAS management area plans for all of the sites.

"They're essentially documents which will advise and inform our remediation strategies."

Defence has confidentially settled one legal claim for PFAS groundwater contamination brought by retired military doctor, Eric Donaldson, who lives next door to the Oakey Army Aviation Base.

Mr Clout said at the current rate, all claims against Defence would be "resolved sometime in the next 200 years".

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