A billionaire climate-change activist has accused New York GOP Chairman Ed Cox of making “false and defamatory” statements about him while discussing a state probe of Exxon, The Post has learned.

Tom Steyer, a California hedge-funder who founded the group Next Gen Climate, had his lawyer send a threatening letter to Cox after objecting to statements the Republican Party chairman made to the Dailycaller.com.

They also sent a complaint to the Daily Caller.

Cox was commenting on state Attorney General Eric Schneiderman’s Exxon probe, which he slammed as a political hit job. Cox also speculated whether Steyer prodded Schneiderman to launch the Exxon probe, which seeks to determine if the oil behemoth violated consumer-protection laws by selling fossil fuels without disclosing its effect on climate change.

“Mr. Cox made false and defamatory statements . . . The media outlet removed Mr. Cox’s false statement from its story after being informed of its grossly inaccurate and defamatory nature,” Steyer spokesman Gil Duran told The Post.

The letter sent to the Daily Caller Foundation in March complained that the quotes attributed to Cox could be interpreted as saying Steyer “made political contributions in exchange for influence, access or favors, which is unethical and/or unlawful.”

Cox, in a written response, did not challenge Steyer’s complaint.