Exxon Mobil sued California’s attorney general, the Sierra Club and other environmental groups on Monday, alleging that they conspired to defame the oil giant and kneecap its business prospects amid a debate over whether plastics can be recycled effectively.

The claims are an escalation in the legal conflict between oil companies and environmental groups, which have spent years fighting over environmental concerns related to fossil fuels, plastics and climate change.

Exxon’s lawsuit singles out language used by Rob Bonta, the California attorney general, who sued Exxon in September, alleging that the company carried out a “campaign of deception” that led people to buy more single-use plastics by promoting the idea that the products could be recycled. Plastics are made from fossil fuels and are more difficult to recycle than other materials like paper and metal. Mr. Bonta’s lawsuit, filed in superior court in San Francisco, denounced the company’s “advanced recycling” program, which refers to processes that break down plastics to create new materials, including fuel.

“Exxon Mobil has not engaged in a decades-long secret mission to brainwash or deceive the public,” the company said in its federal lawsuit, filed Monday in the Eastern District of Texas.

Exxon said Mr. Bonta later made false statements in interviews and other forums about the efficacy of its recycling technology, causing prospective business deals to fall apart. “Advanced recycling is not a ‘farce’ or ‘myth,’” the company said in its suit.