US intelligence services have no reports of Russian killings on British soil – including the death of a businessman it was claimed had been assassinated, an inquest heard.

Alexander Perepilichnyy, 44, died near his home in Weybridge, Surrey, in November 2012, a month after winning a legal claim mounted by a firm linked to a suspect in the killing of Russian defector Alexander Litvinenko, the inquest was told.

Mr Perepilichnyy was being pursued for millions of dollars in Russia, including from a company with links to the alleged killer of ex-Soviet spy Mr Litvinenko.

BuzzFeed news reported after the Skripal case in Salisbury that Russian agents were behind as many as 14 state-sponsored assassinations.

But at an inquest at the Old Bailey on Wednesday, Coroner Nicholas Hilliard QC heard a letter from the US Embassy stated intelligence officials did not have evidence of Russian involvement in plots to kill whistleblowers in the UK.

Two post-mortems failed to find a cause of the businessman’s death, but traces of plant-based poison may have been found in the 44-year-old’s stomach after he had eaten sorrel soup, a previous inquest heard.

Mr Perepilichnyy had been helping specialist investment firm Hermitage Capital Management uncover a $230million (£150 million) Russian money-laundering operation.

A guest sharing the same name as the head of the Russian Secret Service (FSB) was at the hotel in Paris where Perepilichnyy was staying days before he died and where it was alleged he was poisoned, a previous inquest hearing.

Perepilichnyy, an investment specialist, was due to give evidence to a Swiss investigation concerning the theft of $230m (£165m) from Mr Browder’s investment company, Hermitage Capital, by senior tax officials linked to a Russian organised crime gang.

The whistleblower claimed he had been involved in laundering that money and told friends he had received threats shortly before his death.

Judge Hilliard wrote to the then Home Secretary Amber Rudd, asking for details of the review of 14 suspicious deaths which could influence Mr Perepilichnyy’s inquest.

Her successor Sajid Javid signed a Public Interest Immunity (PII) certificate ten days ago which would ban any possible details of Perepilichnyy’s involvement with the British government from being made public at the inquest.

The order would also block any MI5 or Scotland Yard reports about the 14 deaths being made public on the grounds of “national security”.

Andrew O’Connor QC, representing the British government, said a letter from the US Embassy in London had been sent on Tuesday, giving details of a report which included everything the US government knew about Mr Perepilichnyy.

He said: “The report contains no US government reporting of the death of Mr Perepilichnyy, and on that basis it is no longer necessary for the UK government to see it.”

But Henrietta Hill, representing Hermitage Capital, said the letter from the American embassy still left doubts over whether a report existed or not.

She said: “BuzzFeed reported that there was ‘high grade’ intelligence indicating that Mr Perepilichnyy was likely assassinated in direct orders from Mr Putin and those linked to him.

“There was an intelligence report compiled by US national intelligence services which asserted with high confidence his murder was sanctioned by Mr Putin.

“That is the background to those documents.

“The first concern we have is with the reading of that letter.

“The letter states the US government has documentation referencing UK-based public media reports that he was assassinated in the UK.

“We have to question whether the document referred to in this letter from the US contains any US reporting.

“We are struggling to see how that leaves what has been reported by BuzzFeed.

“We have to question whether or not what has been reported by BuzzFeed is accurate or not.

“There’s a US Government report which states there was no US government reporting.

“We remain in the dark as to whether a report exists or not.

“There needs to be clarity and transparency for those I represent as well as the public.”

The hearing then went into a secret “in chambers” session so the judge could hear the UK government’s submission about PII behind closed doors.

The inquest is expected to resume for final submissions later this year.