The Australian government said on Thursday that it was suing 3M for more than $1.4 billion in damages, alleging that the American industrial conglomerate had concealed information about the harmful effects of “forever chemicals” used at more than two dozen military sites across the country.

The lawsuit is the largest ever brought by the Australian government, Michelle Rowland, the country’s attorney general, told reporters in Canberra, the capital.

“This is a government that is prepared to take on one of the biggest multinational corporations in the world,” Ms. Rowland said.

The case is the latest in a wave of legal actions against the Minnesota-based company over contamination linked to PFAS, or per- and polyfluoroalkyl substances. In 2024, 3M agreed to pay $10.3 billion over a decade to public water suppliers in the United States. State and local governments, including those in Minnesota, Alabama and New Jersey, have also sued the company and received settlements.

The so-called forever chemicals — which are called that because they do not break down naturally — have been linked to liver damage, developmental problems, reduced immune function and cancer. They became ubiquitous, used in everything from clothing to the nonstick coating for frying pans to firefighting foam.

That foam was widely used at military bases around the world, both to extinguish fuel fires and during emergency-response training exercises. The U.S. Defense Department has identified 723 installations where PFAS may have been used or released, and Congress has since approved hundreds of millions of dollars to pay for cleanup efforts.

In Australia, PFAS-containing firefighting foams were phased out in 2003 because of environmental concerns, though the Australian Defense Department did not begin its own phaseout until 2004. Before the government stopped using the foams, 28 military sites had been contaminated, according to the lawsuit.

An earlier investigation by Australia’s Defense Department found PFAS contamination was concentrated in areas where the firefighting foams had been used, stored or disposed of. Since 2020, the department has paid out more than $366 million to settle class-action lawsuits related to its use of the foam.

Ms. Rowland said that 3M withheld environmental testing conducted by its own laboratory showing “significant” harmful environmental effects associated with the firefighting foam. She added that the company had said that the foam could be safely disposed of and posed “no significant adverse environmental effect.”

“This misconduct has contributed to substantial costs for Defense and the Australian taxpayer, including over $1 billion to date to investigate, remediate and mitigate PFAS contamination,” she said.

Australia plans to use the $1.4 billion it is seeking in damages to help treat contaminated soil and water and provide alternate water supplies to communities near the military sites, said Peter Khalil, the assistant defense minister.

In a statement, 3M said it planned to fight the case in the legal system, noting it had “never manufactured PFAS in Australia” and that it stopped selling the product at issue in Australia around 20 years ago.

“Despite this, the Department of Defense continued to use PFAS-containing firefighting foams for nearly two decades longer,” 3M said.

In 2022, 3M said it would stop manufacturing PFAS by the end of 2025, while maintaining that the chemicals could be produced and used safely. At the time, the company said its annual net sales from PFAS-related products totaled about $1.3 billion.

Concerns about PFAS contamination extend well beyond military sites.

A New York Times investigation found that 3M scientists in the early 2000s had learned that the toxic chemicals — which the company’s own research had linked to birth defects and cancer — were turning up in sewage that was later spread as fertilizer on farmland across the United States.

In Minnesota, 3M disposed of its manufacturing waste at several sites in the eastern Twin Cities metropolitan area from the 1950s through the 1970s. Minnesota’s attorney general sued the company in 2010, alleging that its disposal practices contaminated drinking water, resulting in an $850 million settlement.