A class action has been filed against the Defence Department over PFAS contamination.

PFAS chemicals were used in firefighting foam on Defence bases for decades, and have now leached into the environment and nearby resident's blood streams in the NT town of Katherine.

Shine Lawyers launched the class action on behalf of the town this week.

“For the people of Katherine affected by PFAS, this action is about accountability and justice,” the firm said in a statement.

“Our research has revealed that PFAS chemicals have been spreading from RAAF Base Tindal for decades, and continues to do so.

“The toxic chemicals amass and persist in the environment and in the human body, and the levels seen in Katherine are exceedingly high and widespread.

“Many people in the community are trying to move their family out of this toxic area, but are stuck, unable to sell their property.”

The Department of Defence has denied a link between PFAS exposure to human disease.

Shine Lawyers says it has evidence the chemical has adversely affected residents' wellbeing.

“Exposure to these toxic chemicals have been linked to immune dysfunction, hormonal interference, thyroid disruption and certain types of cancer,” they said.

“It follows an investigation that revealed that thousands of Katherine locals had been exposed to toxic chemicals, which have permeated land and water supplies, food sources, and bloodstreams, with potentially catastrophic consequences.”

The Department of Defence should file its defence in coming months.