The foreign secretary faces new questions over his involvement in a £161,000 donation by the wife of Vladimir Putin’s former finance minister to the Conservative party in the wake of the poisoning of former Russian spy Sergei Skripal.

In 2014, Boris Johnson and David Cameron played a tennis match with Lyubov Chernukhin, whose husband worked for Putin until 2004, in return for a large donation to CCHQ.

When details of the deal emerged Cameron was forced to publicly defend the pair’s actions and denied he had taken money from a “Putin crony”. Cameron argued Russian oligarch Vladimir Chernukhin is no longer associated with Putin’s inner circle, but he has repeatedly been described as Putin’s protégé and earned his fortune managing some of Russia’s biggest businesses including Aeroflot, the Russian development bank (VEB), and the Russian Agricultural Bank (RSHB). He personally received the Order of Honour from Vladimir Putin in 2004.

More recently, Chernukhin was nominated a non-executive director of Polyus Gold International Limited in 2013 by billionaire Zelimkhan Mutsoev, who has been a member of the State Duma, the lower house of the Russian parliament, since 1999.

Boris Johnson has come under fire in recent weeks after he misattributed quotes to scientists at the Porton Down military laboratory over the poisoning of Sergei Skripal. In an interview with German broadcaster Deutsche Welle (DW), Johnson said: “When I look at the evidence, the people from Porton Down, the laboratory…they were absolutely categorical, I mean, I asked the guy myself, I said, ‘are you sure?’ and he said ‘there’s no doubt.’ And so, we have very little alternative but to take the action that we have taken.”

However, Porton Down, officially known as the Defence Science and Technology Laboratory (DSTL), has since released a statement that casts doubt on the foreign secretary’s certainty about the source of the nerve agent. In an interview with Sky News, DSTL chief Gary Aitkenhead said: “We were able to identify it as Novichok, to identify that it was military-grade nerve agent.

“We have not identified the precise source, but we have provided the scientific info to government, who have then used a number of other sources to piece together the conclusions you have come to…It is our job to provide the scientific evidence of what this particular nerve agent is, we identified that it is from this particular family and that it is a military grade, but it is not our job to say where it was manufactured.”

Johnson has been accused of trying to use the poisoning of the Russian spy in Salisbury to smear Labour leader Jeremy Corbyn in an attempt to deflect questions about Russian money flooding into the Conservative party in recent years. Johnson has called Corbyn a “useful idiot” for the Kremlin, but it is the Tories who have reportedly accepted an estimated £800,000 in donations from Russian sources. Such large sums flowing into British politics from foreign sources is cause for serious concern, especially with news that Johnson was specifically targeted by members of Russian intelligence as part of their effort to obtain political influence in Britain.

In an interview with Andrew Marr last month, Johnson struggled to explain why the Conservatives had blocked a Labour motion to implement a British version of the so-called Magnitsky Act that sanctions wealthy individuals with ties to the Kremlin. In an attempt to deflect the question, Johnson called the amendments, which might affect some influential billionaires and political donors, “unsuitable“.