Relations between the UK and Russia were under fresh strain on Friday after Jeremy Hunt warned the Kremlin not to use people as “diplomatic pawns” following the arrest of a British citizen on spying charges.

The foreign secretary confirmed that the UK had offered consular assistance to the former US marine. According to Russian media, British embassy staff have also requested access to him.

Mr Whelan, who was initially identified only as an American citizen after he was detained last week, also holds Irish citizenship.

Speaking during a formal visit to Singapore, Mr Hunt told Sky News that “individuals should not be used as pawns of diplomatic leverage”.

“We need to see what these charges are against him and understand whether there is a case or not,” Mr Hunt said.

“We are giving every support we can, but we don’t agree with individuals being used in diplomatic chess games.

We are giving every support we can, but we don’t agree with individuals being used in diplomatic chess games Jeremy Hunt, British foreign secretary

“Because it is desperately worrying, not just for the individual but their families, and we are all extremely worried about him and his family as we hear this news.”

Thursday’s disclosure of Mr Whelan’s multiple nationalities has added a further layer of complexity to his case – and tension to an already overextended UK-Russia diplomatic relationship.

Mr Hunt said that the US was taking the lead on the case. “The US are leading on this because he is a British and American citizen,” Mr Hunt said.

Relations remain at rock bottom following the nerve agent poisoning of Russian double agent Sergei Skripal and his daughter – and the subsequent fallout.

In the months that followed the Salisbury attack, Russia was hit with unexpected, European-wide diplomatic expulsions, sanctions, the identification of two Russian military intelligence officers as the main suspects, and the largely unintended identification of hundreds of others.

In his annual press conference in late December, Mr Putin said he remained open to improving relations. Privately, Kremlin officials are resigned to relations deteriorating further.

Mr Whelan, 48, was arrested last Friday by officers of Russia’s security agency, and on Thursday charged with espionage. His multiple citizenships add to an altogether quirky biography.

Born in Canada to British parents, he was discharged dishonourably from the military in 2008, after which he made a career out of security analysis. He was by all accounts a Russophile and, judging by social media entries, a vehement supporter of US president Donald Trump.

And he also holds Irish citizenship. “The Embassy of Ireland in Moscow has requested consular access to an Irish citizen currently detained in Russia after receiving a request for assistance,” a Department of Foreign Affairs spokesperson told The Independent on Friday.

“The Department of Foreign Affairs and Trade will provide all possible and appropriate assistance in relation to this case.”

Mr Whelan also made a number of trips to Russia since 2006, but friends and family insist he did so as an ordinary citizen.

In a statement on Twitter, his twin brother David Whelan said he travelled to Moscow for the wedding of a fellow former marine. His innocence was “undoubted”.

The danger is there is no such thing as justice in the Russian criminal system, either for Russians or foreign nationals. The UK should work in concert with EU and NATO allies to secure his release Chris Bryant MP, member of the Foreign Affairs Select Committee

Mr Whelan’s arrest came two weeks after Russian citizen Maria Butina pleaded guilty to conspiring to act as a foreign agent in the US. The timing has fuelled speculation that Moscow may, in fact, be using Mr Whelan as leverage for a swap.

On Thursday, Mr Whelan was served unspecified espionage charges carrying custodial sentences of between 10 and 20 years.

Foreign Affairs Committee member Chris Bryant MP said: “Russia seems to be up to its usual tricks. The danger is there is no such thing as justice in the Russian criminal system, either for Russians or foreign nationals. The UK should work in concert with EU and Nato allies to secure his release.”

Speaking with a state news agency, his state-appointed lawyer, Vladimir Zherebenkov, confirmed he had pleaded innocent to the charges. The lawyer added weight to rumours by suggesting a swap was a solution to Mr Whelan’s problems.

But the news that his client is, in fact, a citizen of multiple states would seem to make that prospect more complicated.

If, as now seems likely, the case reaches court, the former marine should not hope for a positive outcome. Fewer than 0.1 per cent of cases in Russian courts end with acquittals.

Dutch security services expel Russian spies over cyber plot Show all 23 1 /23 Dutch security services expel Russian spies over cyber plot Dutch security services expel Russian spies over cyber plot Russian passports belonging to (top row) Oleg Sotnikov (left), Aleksei Morenets, (bottom row) Evgenii Serebriakov (left) and Alexey Minin, who have been named as the four GRU officers who tried to hack the global chemical weapons watchdog which is investigating the Salisbury nerve agent attack PA Dutch security services expel Russian spies over cyber plot On April 13 the officers parked a car carrying specialist hacking equipment outside the headquarters of the OPCW in The Hague Dutch Ministry of Defence/PA Dutch security services expel Russian spies over cyber plot Specialist equipment intended for the alleged hacking of WiFi networks of the Organisation for the Prohibition of Chemical Weapons (OPCW). Russia's military intelligence service has been accused of trying to hack the global chemical weapons watchdog which is investigating the Salisbury nerve agent attack PA Dutch security services expel Russian spies over cyber plot The Dutch counter-terrorism officers intervened to disrupt the operation and the four GRU officers were ordered to leave the country Dutch Ministry of Defence/PA Dutch security services expel Russian spies over cyber plot Mobile phones and a camera recovered from four GRU officers who were alleged to have hacked the WiFi networks of the Organisation for the Prohibition of Chemical Weapons (OPCW) PA Dutch security services expel Russian spies over cyber plot The four Russians arrived on diplomatic passports Netherlands Defence Ministry Dutch security services expel Russian spies over cyber plot Alexey Minin, who has been named as one of the four GRU officers who tried to hack the global chemical weapons watchdog which is investigating the Salisbury nerve agent attack PA Dutch security services expel Russian spies over cyber plot A car carrying hacking equipment used by GRU officers, travelling on official Russian passports, parked near the headquarters of the OPCW in The Hague Dutch Ministry of Defence/PA Dutch security services expel Russian spies over cyber plot Oleg Sotnikov, who has been named as one of the four GRU officers PA Dutch security services expel Russian spies over cyber plot Hacking equipment belonging to four Russian officers Dutch Ministry of Defence/AP Dutch security services expel Russian spies over cyber plot Evgenii Serebriakov, who has been named as one of the four GRU officers PA Dutch security services expel Russian spies over cyber plot Equipment found in possession of four Russian citizens Reuters Dutch security services expel Russian spies over cyber plot Photos of the Organisation for the Prohibition of Chemical Weapons (OPCW) and its surroundings taken on the 11 April, found on the phone of GRU officer Alexey Minin Dutch Ministry of Defence/PA Dutch security services expel Russian spies over cyber plot Equipment found in possession of four Russian citizens REUTERS Dutch security services expel Russian spies over cyber plot Aleksei Morenets, who has been named as one of the four GRU officers PA Dutch security services expel Russian spies over cyber plot Undated handout photo dated issued by the Dutch Ministry of Defence of a car carrying hacking equipment used by GRU officers, travelling on official Russian passports, parked near the headquarters of the OPCW in The Hague. PRESS ASSOCIATION Photo. Issue date: Thursday October 4, 2018. On April 13 the officers parked a car carrying specialist hacking equipment outside the headquarters of the OPCW in The Hague. At that point the Dutch counter-terrorism officers intervened to disrupt the operation and the four GRU officers were ordered to leave the country. See PA story POLITICS Russia. Photo credit should read: Dutch Ministry of Defence/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. Dutch Ministry of Defence Dutch Ministry of Defence/PA Dutch security services expel Russian spies over cyber plot A combo of a taxi bill and a map, with a ride from a street next to the Main Directorate of the General Staff of the Armed Forces of the Russian Federation, GRU, to Sheremyetevo airport in Moscow, found in possession of one of four GRU officers AP Dutch security services expel Russian spies over cyber plot Yevgeny Serebryakov, an alleged Russian agent AFP/Getty Dutch security services expel Russian spies over cyber plot Dutch security services say they have foiled an attempted cyber attack targeting the international chemical weapons watchdog, during its investigations into the Salisbury attack. Netherlands Defence Ministry Netherlands Defence Ministry Dutch security services expel Russian spies over cyber plot Dutch security services say they have foiled an attempted cyber attack targeting the international chemical weapons watchdog, during its investigations into the Salisbury attack. Netherlands Defence Ministry Netherlands Defence Ministry Dutch security services expel Russian spies over cyber plot Dutch security services say they have foiled an attempted cyber attack targeting the international chemical weapons watchdog, during its investigations into the Salisbury attack. Netherlands Defence Ministry Netherlands Defence Ministry Dutch security services expel Russian spies over cyber plot Dutch security services say they have foiled an attempted cyber attack targeting the international chemical weapons watchdog, during its investigations into the Salisbury attack. Netherlands Defence Ministry Netherlands Defence Ministry Dutch security services expel Russian spies over cyber plot Dutch security services say they have foiled an attempted cyber attack targeting the international chemical weapons watchdog, during its investigations into the Salisbury attack. Netherlands Defence Ministry Netherlands Defence Ministry

The information surrounding the case is murky and in many respects barely plausible.

Several days after his arrest, the only complete account of Mr Whelan’s arrest appeared on Rosbalt, a St Petersburg-based wire agency with clear links to the security services. It claims Mr Whelan was arrested in a hotel room after being handed a USB flash drive by a Russian man “he had known for some time” and was “trying to recruit”.

The former marine had developed an “unusual” research technique, it somewhat bizarrely added, by “connecting to local Russian men on local social media”.

The aim of these meetings was to obtain information on the security services, the publication suggested.

But oddly for a sting operation of this kind, state media have paid little attention to the story.

As yet, no video evidence or photos have been released. This would appear to be an unexpected oversight given that “spies” captured in Russia usually become overnight state TV stars.

It may well indicate the operation was not wholly sanctioned at the top, or that there is confusion about what to do next.

While state media has remained unusually quiet on the affair, loyalist Russian commentators have latched on his biography to paint a picture of a career spy.

“So this is how it is,” wrote Igor Korotchetkov, an analyst linked to the Russian Ministry of Defence. “The US citizen arrested for espionage also has British citizenship. This means he not only worked for CIA but MI6 too?”

Following his arrest, Mr Whelan was transferred to Lefortovo detention centre, one of Russia’s most notorious and draconian prisons. He will stay there until at least 28 February, a court has ruled. The first 10 days of this will be spent in solitary confinement.

Apart from that, little is known about his detention conditions, says Yevgeny Yenikeev, a member of the Public Oversight Commission, an independent NGO monitoring detention conditions.

While Lefortovo prison is undergoing a refurbishment programme, large parts of it remain without hot water or private toilets. Buckets leading to holes in the ground are a grim and unhygienic reality in many cells.

Given the fact that the prison is almost full, it is likely he will have been placed “wherever there is room” – toilet or no toilet.