Sensitive material that could reveal if a Russian millionaire was working with British spies before he died will not be made public at his inquest, a coroner has ruled.

Sajid Javid lodged a secrecy application at the inquest into the death of Alexander Perepilichnyy citing national security concerns. The 44-year-old collapsed and died while jogging near his home in Weybridge, Surrey, in 2012.

Lawyers acting for the life insurers Legal & General told the Old Bailey the businessman could have been “rubbed out” if he was working for British spies and that evidence of any links to UK intelligence services could show he was in “special danger”.

Andrew O’Connor QC, for the government, said the disclosure of sensitive material raised a “real risk of serious harm to one or more public interests”.

The coroner, Nicholas Hilliard QC, heard details of the home secretary’s public interest immunity (PII) application in private in June. In a written ruling, the coroner said the documents in question were not required for the inquest.

“[The PII material’s relevance] is so marginal and/or minimal as to mean that it will afford me no assistance in resolving the central question in this inquest as to how Mr Perepilichnyy died,” he said.

Hilliard has been examining whether the wealthy executive was murdered with poison or died of natural causes.

The coroner said he had considered whether the material contained anything “which was not otherwise publicly available” and had “significant bearing on or connection with” the issues he had to decide upon. “I am satisfied here that the answer to both questions is no,” he said.

Before his death, Perepilichnyy had been helping the UK-based campaigner Bill Browder’s Hermitage Capital investment fund to expose a $230m money-laundering operation.

Bob Moxon Browne QC, for Legal & General, told the court his concern about Javid’s application was “whether or not British police or the government have evidence that Mr Perepilichnyy was, prior to his death, working for or in contact with British intelligence”.

He argued there should be an exception to the rule of neither confirming nor denying contact with security services in Perepilichnyy’s case.

Moxon Browne cited the poisoning of the former double agent Sergei Skripal in Salisbury in March as demonstration of “the lengths to which the Russian state are prepared to go to make an example or punish people perceived as enemies, traitors or turncoats”.

He said the public was told of Alexander Litvinenko’s role with British intelligence after he was fatally poisoned.

If it also was true in the case of Perepilichnyy, it would be, he said, “very powerful evidence indeed that he might have been in special danger from those who wish him ill because of the perception he was a traitor or a turncoat or enemy of Russia”.

The inquest had also heard how Buzzfeed reported that high-grade US intelligence indicated that Perepilichnyy was likely assassinated on direct orders of Vladimir Putin or those close to him.

No application was made for American intelligence to be withheld, after the US dismissed the claims.

The inquest is due to continue on Friday.