Rep. Dana Rohrabacher (R-CA) speaks during a House Foreign Affairs Europe, Eurasia and Emerging Threats Subcommittee hearing. Aaron P. Bernstein/Reuters

A new complaint filed by investor Bill Browder with the Treasury's Office of Foreign Asset Control alleges that California Rep. Dana Rohrabacher and his staff director, Paul Behrends, violated US sanctions when they accepted anti-Magnitsky Act material from the Russian prosecutor's office and used it to try to undermine the legislation in Washington.

Browder, who spearheaded the passage of the Magnitsky Act in 2012, said Rohrabacher's anti-Magnitsky efforts amounted to providing a service to Russia's deputy prosecutor general Victor Grin, who was sanctioned as part of the Magnitsky Act and would benefit from its repeal.

Rohrabacher's spokesman, Ken Grubbs, responded to the complaint Tuesday morning, characterizing Browder's OFAC filing as an attempt to obfuscate Russia's side of the story and slamming the wealthy investor as "a billionaire tax exile."

"Why would a billionaire tax exile want to prevent a US congressman from receiving both sides of an issue currently before Congress?" Grubbs said. "It may not be in the interest of some individuals for the Russian side of serious matters to be examined and evaluated. Attempts to intimidate a member of Congress not to look at both sides is suspicious in and of itself."

Browder, the founder of Hermitage Capital Management, renounced his US citizenship in 1998 and moved to Russia, where he quickly became the country's most successful foreign investor. He was convicted of tax evasion in absentia by a Moscow district court in 2013, one year after spearheading the Magnitsky Act — a sanctions package that infuriated Russian President Vladimir Putin, who retaliated by banning Americans from adopting Russian children.

The Act, signed into law by President Barack Obama in 2012, was designed to punish Russian officials suspected of being involved in the death of Browder's accountant, Sergey Magnitsky.

Magnitsky is believed to have uncovered a $230 million tax fraud scheme in 2008 when he was working for Hermitage that implicated high-level Kremlin officials and allies of President Vladimir Putin. He was later thrown in jail by the same Interior Ministry officers he testified against during criminal proceedings to punish those involved in the tax scheme, Browder said in 2015, and died in custody after being held for 358 days.

A human-rights commission in Russia found that Magnitsky had been illegally arrested and beaten to death. The Kremlin maintains that he died of a heart attack.

Browder filed the OFAC complaint on the heels of a Daily Beast report published last week which said that Rohrabacher, a staunch defender of Russia and Putin, accepted a "confidential" document from the prosecutor general’s office in Moscow in April 2016 which he then used to try to undermine the Magnitsky Act on Capitol Hill.

Browder alleged in the complaint that Rohrabacher provided "services" to Russia's deputy general prosecutor, Victor Grin, by attempting to stymie an expansion of the Magnitsky Act being deliberated in Congress last summer.

The complaint says Rohrabacher "made personal introductions for lobbyists advocating the Russian government's and Grin's position against the Magnitsky Act." Those people, according to the complaint, include Russian lawyer Natalia Veselnitskaya and Russian-American lobbyist Rinat Akhmetshin — both of whom attended a meeting with Donald Trump Jr. at Trump Tower last June to discuss a possible repeal of the Magnitsky Act.

Reached for additional comment on Grubbs' statement, Browder said that in spite of seeing "documentary evidence showing that Sergei Magnitsky was murdered," Rohrabacher "has been knowingly spreading false information from the Kremlin that Sergei died of natural causes in order to assist certain sanctioned Russian individuals who want to get off the Magnitsky list."

Browder, who called Rohrabacher's actions last summer "brazen" violations, added that is behavior is "not consistent with his role as a US Congressman" and needs to be "examined thoroughly and fearlessly."