Montpelier — The state of Vermont is suing Volkswagen and its subsidiaries, claiming the car company committed a massive fraud, broke environmental laws and that a proposed settlement of $3 million offered in June to address consumer complaints was “wholly inadequate.”

Attorney General Bill Sorrell held a news conference on Thursday to announce the lawsuit in Vermont Superior Court and condemn the company for conducting “a massive and intentional fraud” when it advertised “clean” and “green” vehicles to Vermonters.

The company admitted in September 2015 that it advertised cars as clean diesel but in fact built them with equipment called “defeat devices” designed to cheat on emissions tests. The company also allegedly manipulated the cars’ diagnostic equipment to conceal those defeat devices.

Approximately 3,400 affected Volkswagens, Audis and Porches with 2-liter and 3-liter engines are registered in Vermont, Sorrell said. That’s the second-highest number of affected cars per capita of all the states in the country, behind Oregon.

A spokesperson for the company said in a statement: “Volkswagen is committed to reaching a fair and efficient resolution of remaining federal and state diesel claims in the United States.”

“We have received Vermont’s complaint, and will respond appropriately,” the spokesperson said.

Sorrell said Vermont is serious about its complaint.

“This was not a mistake,” he said. “This was not a ‘whoops’ situation. This was intentional fraud on a massive scale. We look forward to our day in court and to prove their liability, prove how we’ve been harmed in the state, and see that justice is done.”

Vermont’s case alleges an extensive coverup that was openly discussed the company’s executives and charges the company and its subsidiaries with nine violations of state law, including Vermont’s clean air laws and the Vermont Consumer Protection Act.

Filing the lawsuit means that Vermont has rejected $2.9 million that the company offered if the state agreed not to sue under the Consumer Protection Act. Sorrell said he is not seeking a specific amount of money, but there could be thousands or hundreds of thousands of violations, which each carry a fine of $10,000.

“With all due respect to those state and federal officials who negotiated the proposed national settlement, we just find the consumer protection arena inadequate,” Sorrell said. “We think the nature of the conduct, the impact on Vermonters, the amount of advertising — the false advertising—in Vermont, deserves stiffer penalties.”

While some states have sued for either consumer protection or environmental issues, the lawsuit makes Vermont just the second state to sue Volkswagen under both its consumer protection laws and environmental laws. The other state is New Jersey, which sued in February.

Vermont always has retained the right to sue Volkswagen under its own clean air laws, Sorrell said, because Vermont has a federal legal designation as a state with more-stringent environmental standards than the U.S. Environmental Protection Agency.

Filing the lawsuit under Vermont’s clean air laws also does not affect the state’s ability to accept up to $17.8 million from a separate environmental settlement, which was set up as a federally managed trust fund for states to use for specific emission-reduction purposes.

Deb Markowitz, the secretary of the Agency of Natural Resources, said the federal government negotiated that environmental settlement with big cities in mind, but Vermont wanted changes because it also gets diesel emissions from sawmills and farm equipment.

Even though Vermont gets diesel emissions from different sources, she praised residents for choosing to drive clean cars, and she said their choice to drive clean cars helps the state meet regulations from the Environmental Protection Agency.