The Australian government is suing US manufacturing giant 3M for AU$2bn in damages (US$1.4bn; £1.1bn) over its alleged use of toxic "forever chemicals" in firefighting foam that contaminated dozens of defence bases across the country.

It is the largest legal claim ever brought by the government, Attorney-General Michelle Rowland said, as it seeks to recoup the "substantial costs" in dealing with the chemicals - known as PFAS - at 28 locations.

It claims 3M withheld and misrepresented details about the foam and its environmental impact, assuring them it was safe, despite knowing otherwise.

In response, 3M said it has never made PFAS in Australia and stopped selling the foam there 20 years ago.

In announcing the legal action on Thursday, Rowland said the government was committed to holding 3M and 3M Australia to account "for the economic and environmental harms associated with PFAS contamination".

"This misconduct has contributed to substantial costs for defence and the Australian taxpayer, including over $1bn to date to investigate, remediate and mitigate PFAS contamination at defence estate sites," she said.

"Make no mistake, this legal action against 3M is significant."

PFAS - also known as per- and poly-fluoroaklyl substances - are known for their water-resistant and non-stick properties and can be found in firefighting foams, mobile phones, clothing and non-stick cooking pans.

The chemicals do not break down under normal environmental conditions and research has shown the toxins are in dangerous concentrations in water, soil and food and can also linger in the body.

In 2022, 3M said it would stop making and using PFAS amid concerns the substances were linked to a range of health problems including cancer.

Australia's case alleges 3M withheld information and misrepresented the effects of 3M's aqueous film-forming foam (AFFF) including the environmental risks of the foam.

3M also failed to fully disclose what it knew about the environmental risks of the foam and gave assurances about disposal and environmental safety that were inconsistent with what the company knew at the time, the government alleged.

A spokesperson for 3M said it would "defend ourselves against these claims through the legal process".

The company said the Department of Defence kept using the PFAS-containing firefighting foams for two decades after it stopped selling the product in Australia.