The Russian government has hatched a sensational plot to kidnap a prominent British businessman and smuggle him out of the country, it has been claimed.

Newly lodged court documents, seen by the Observer, allege that Russian criminal syndicates working with the Kremlin planned to abduct London-based Bill Browder, who is mired in a wrangle with the Putin regime over the controversial death of a whistleblower.

Browder, chief executive of a British-based investment fund, Hermitage Capital Management, hired as his lawyer Sergei Magnitsky, who went on to expose a tax fraud worth £144m, the biggest in Russian history. After making accusations against interior ministry officials, Magnitsky was arrested. He died in police custody five years ago after being denied medical care. Instead of ordering a proper investigation into Magnitsky’s murder, the Kremlin allegedly covered it up.

Documents submitted to the US district court, southern district of New York, on Friday night have revealed details of the alleged rendition attempt for the first time. A witness statement by Browder, submitted in a legal case involving the whereabouts of money from the tax fraud, reads: “A representative of the US attorney’s office reached out to me and explained that the office had received confidential information that unknown persons were soliciting contributions to a fund intended to hire private investigators to find me and return me to Russia.

“By this point, I and multiple Hermitage personnel and lawyers had been either forcibly ejected or run out of Russia due to credible threats against us.

“Consequently, when the US attorney’s office informed me of their source’s warning, I was alarmed. I understood the information they provided as a specific, credible threat that the Russian criminal enterprise – likely aided by the Russian government and/or secret police – were planning to kidnap and organise a rendition operation against me abroad.”

In 2013 the Russian authorities put Magnitsky posthumously on trial. They also convicted Browder and sentenced him to nine years in absentia. Browder has been pursued ever since, with the Russian authorities already applying twice to Interpol for his arrest. Both attempts were rejected as politically motivated.

However, the Russian president, Vladimir Putin, has made a third attempt to use the Interpol red notice system to apply for the arrest of Browder; this is currently being considered by the crime agency.

Browder’s campaigning over the death of Magnitsky, who was 37, led the US Senate to pass a bill – the Magnitsky Act – in 2012 banning Russian officials accused of human rights abuses from travelling to the country. “It seems that Putin was so angry at me for getting the Magnitsky Act passed that he’s instructed his special services to use all possible channels to get me back to Russia, including Interpol and illegal rendition,” said Browder.