The White House has confirmed that President Donald Trump and President Vladimir Putin discussed striking a deal that would allow Russia to criminally investigate a former US ambassador.

The Kremlin has accused financier and activist Bill Browder and his alleged associates of committing tax fraud and campaign finance violations, which the US state department says are baseless.

Browder is the force behind the Magnitsky Act, which freezes the assets and bans travel of some high-level Russian officials.

In her Wednesday afternoon press briefing, White House press secretary Sarah Sanders confirmed that President Donald Trump and President Vladimir Putin discussed striking a deal that would allow Russia to interview and possibly prosecute a former US ambassador.

In what Trump called "an incredible offer," Putin would allow special counsel Robert Mueller's prosecutorial team to go into Russia to conduct interviews with Russians indicted of hacking in the US, in exchange for Russia being allowed to interview 11 American citizens. This list includes former US ambassador to Russia Michael McFaul, who Russian state media said is part of a criminal investigation into alleged crimes committed by financier Bill Browder, though is more likely linked to accusations he stirred up unrest during his ambassadorship.

The Kremlin has also accused Browder of committing tax fraud and illegally contributing $400,000 to Hillary Clinton's campaign, allegations largely thought to be meritless.

While US State Department spokeswoman Heather Nauret called Russia's allegations against Browder "absurd" and the interviewing of a former diplomat a "grave concern," Sanders didn't rule out the possibility of the deal, and said Trump will discuss it with his national security team.

"The fact that they want to question 11 American citizens, and the assertions that the Russian government is making about those American citizens — we do not stand by those assertions," said Nauret.

'Lodged under Putin's skin'

Browder, who has been banned from Russia since 2005, says he is "lodged so firmly under Putin's skin" over a series of laws he helped get passed around the world that hit the bank accounts of many high-level, powerful Russians, and is believed to have affected foreign assets tied to much of Putin's personal wealth.

"Putin almost never utters the names of his enemies — except for mine, which he lately seems to utter at every opportunity. To my mind, this can only mean that he is seriously rattled," Browder wrote in TIME Magazine.

The Magnitsky Act is named for Browder's former tax lawyer Sergei Magnitsky, who Browder alleges was jailed and beaten to death after uncovering a $230 million tax fraud scheme involving Kremlin officials and associates of Putin. Magnitsky laws freeze the assets and deny travel visas for high-level Russian officials suspected of committing human rights abuses.

For Putin, Browder described repealing Magnitsky laws around the world as "perhaps his largest foreign policy priority. But none of his efforts have worked. Not only has it not been repealed, it’s spread to six additional countries."

Browder additionally notes that his Magnitsky Global Justice campaign has successfully located the $230 million, resulting in active law enforcement investigations around the world and millions in Russian assets frozen.

Last July, the Kremlin-linked lawyer and lobbyist Natalia Veselnitskaya met with several high-level Trump campaign officials. She promised damaging information on Hillary Clinton, but used the meeting to lobby against the Magnitsky Act.

"In essence, Putin received some of the proceeds of this crime, and he is terrified that the Magnitsky Act could be applied to his offshore fortune, which is probably one of the largest amassed in modern times," Browder continued.

Browder himself was born in the US but is now a British citizen and lives in the UK, meaning he is wholly outside of Trump's jurisdiction. His alleged associates, including McFaul, are not.

'Cold War, Hot Peace'

The reported inclusion of McFaul, a former US ambassador and public servant, among the people who could be interviewed and prosecuted by Russia as part of the potential deal was particularly shocking to diplomats and international relations experts.

"This is stunning, outrageous and very very dangerous. The thought that the president would commit to even considering turning a former US Ambassador over to Russia — in connection with his federal service, no less — is amazing even for this administration. Where is Congress?!" tweeted Walter Shaub, the former director of the Office of Government Ethics.

McFaul, who served as ambassador between 2012 and 2014, recounted in his memoir "Cold War, Hot Peace" how he became the scapegoat for protests Putin faced after being elected president.

In an excerpt of the book published in The Washington Post, McFaul wrote that Russia launched, a "full-scale disinformation campaign alleging that, under my direction, the United States was funding the opposition and attempting to overthrow Putin."