Billionaire environmental activist Tom Steyer spoke out on Wednesday in support of an unconfirmed investigation by California into allegations that ExxonMobil spent decades lying to investors and the public about its knowledge of climate change.

“We don’t have the facts yet, but I think that there is enough that has been revealed that it’s totally appropriate that (California) be conducting this investigation,” Steyer told the Guardian. “Anybody who puts out intentionally misleading information I think should be answering to us.”

Steyer’s comments came hours after the Los Angeles Times reported that California’s attorney general, Kamala Harris, is looking into what ExxonMobil, the world’s biggest oil company, knew about climate change going as far back as the early 1980s.

Harris’s office declined to comment on the report, writing in an email: “We can’t comment on any ongoing or potential investigation,” according to press secretary Rachele Huennekens.

Previously published reports suggest ExxonMobil may have spent millions over 27 years to publicly promote opposition to climate change science while privately basing strategies and business models around it.

The Guardian reported in July on a company email from Exxon’s in-house climate expert that provided evidence that the company was aware, over a generation ago, of the connection between fossil fuels and climate change, and the potential for carbon-cutting regulations that could hurt its bottom line. It may have factored that knowledge into its decision about a large gas field in southeast Asia. The field, off the coast of Indonesia, would have been the single largest source of global warming pollution at the time.

New York’s attorney general is also conducting a similar probe into ExxonMobil based on previously published reports by the Los Angeles Times and the Columbia University Energy and Environmental Reporting Fellowship.

But, Steyer said, California, as the “largest and most populous state” offers a “particularly strong platform” to increase the reach of any investigation.

“I’m not a lawyer but I believe the laws in California are different and give our attorney general a lot of leeway in terms of how she approaches it,” he said.

RL Miller, chair of the California Democratic party’s environmental caucus, added that the Los Angeles and Ventura Democratic party recently passed a resolution she wrote calling on Harris to investigate ExxonMobil. Harris is currently running for US Senate and will seek the party’s endorsement during its February convention.

“I wanted to bring it up with Democrats because if she wants the Democrats’ endorsements, she needs to listen to Democrats,” said Miller of her outreach to Harris.

Like other climate change activists, Steyer also linked ExxonMobil’s alleged cover-up to similar scandals in the tobacco industry, which for many years fought to deny the negative health effects of smoking.

With climate change, “there is obviously a gigantic impact on the entire world and all the people of the world”, said Steyer. “It’s a society being misled.”