Security officials are deeply concerned that the Kremlin may reveal the identities of British intelligence officers in the escalating and bitter confrontation following the Salisbury nerve agent attack, The Independent has learned.

The disclosure could start, it is feared, with those who work for MI6 among the 23 British diplomats being thrown out of Moscow in retaliation for the same number being expelled from the UK. Doing so would break standard protocol in place to protect spies from opposing sides, in recognition that exposing personal details may put them in danger including from terrorist attacks.

It has been the normal practice since the end of the Cold War to avoid leaking such information in these circumstances. The UK has not published the names of the 23 Russians who have been expelled and there are no plans to do so. Some senior members of Vladimir Putin’s administration are, however, incensed by what they consider to be aggressive and inflammatory remarks made by British ministers about Russia’s culpability over the attempted assassination of former spy Sergei Skripal and his daughter Yulia and are said to be advocating drastic action.

The media in the UK are requested to and generally adhere to the Sensitive Persons Information (SPI) agreement under which personal details of members of security, intelligence and counter-terrorist agencies, as well as special forces and the MoD are not put in the public domain.

But it is acknowledged that it would be impossible to keep these details totally secret in the days of the internet should the Russians choose to reveal them. There is also the worry that Moscow may want to carry out a wider dissemination of British security and intelligence information, possibly using a platform like WikiLeaks which had, in the past, been used to expose Western secrets.

WikiLeaks was also used to release 20,000 Democratic National Committee emails during the US presidential election campaign to undermine Hilary Clinton and help Donald Trump. The US President’s links with Moscow are currently under investigation by special counsel Robert Mueller.

Attempts by the UK to organise concerted international action against Moscow have, so far, been largely unsuccessful. Despite expressions of solidarity from the European Union there have been no moves for further sanctions.

Jean-Claude Juncker, the European Commission President, has congratulated Mr Putin on his re-election and has urged closer ties between the European Union and Moscow. And, in a major blow to Theresa May’s government, Donald Trump sent his own congratulations to Russia’s President, while at the same time pointedly failing to raise the issue of the Salisbury attack.

Mr Trump, presented by Tory right-wingers as the most staunch ally of post-Brexit Britain, ignored the warnings of his national security advisors whose briefing material, it has been reported, said in capital letters “DO NOT CONGRATULATE”. He also dismissed suggestions that he should make clear the US’s concerns over the nerve agent attack. The President described his conversation with Mr Putin as a “very good call.”

The British government is still threatening to take unilateral punitive measures against Russia. Appearing before the Commons Foreign Affairs Committee, Boris Johnson repeated his charge that Mr Putin was responsible for the Salisbury attack, saying: “The trail of responsibility for the assassination does lead inexorably back to the Kremlin. No matter how exactly it came to be done, the path of responsibility goes back to those at the top.” The poisoning, he added, was “a sign” from Mr Putin that “no one could escape the long arm of Russian revenge.”

Mr Johnson wanted to stress that investigations were continuing into wealthy Russians in the UK over possible economic crimes. The Foreign Secretary had taken £160,000 in donation to the Conservative Party for playing tennis with the wife of one of Mr Putin’s former ministers, and the same woman had also donated £30,000 to the party in return for having lunch with Defence Secretary Gavin Williamson. Mr Johnson had defended receiving the money, saying: “It’s very important that we do not allow a miasma of suspicion about all rich Russians in London to be created.”

A senior Whitehall official stated that Russian threats to disclose the identities of British intelligence officers were “utterly unjustified and irresponsible. They know we did not make public the names of those working under diplomatic credentials we expelled from this country. That list was carefully calibrated and we intend to maintain channels of communication.”

Skripal attack aftermath – in pictures Show all 15 1 /15 Skripal attack aftermath – in pictures Skripal attack aftermath – in pictures Scene of attack Members of the emergency services in hazard suits fix the tent over the bench where Sergei and Yulia Skripal were found unconscious on a park bench in Salisbury in March 2018. Getty Skripal attack aftermath – in pictures Victim - Sergei Skripal The retired Russian colonel and former double agent for MI6 was in a critical condition in hospital for more than two months after being exposed to novichok in Salisbury. He was given refuge in the UK after being jailed in Moscow for treason. Mr Skripal came to Britain as part of a high-profile “spy swap” in 2010 in which four men were exchanged for ten Russian "sleeper agents" in the US. In this image he is speaking to his lawyer from behind bars in Moscow in 2006. AP Skripal attack aftermath – in pictures Victim - Yulia Skripal Yulia Skripal was struck down by a novichok poison alongside her father Sergei. Facebook Skripal attack aftermath – in pictures Scene of attack A police officer stands guard outside a branch of the Italian chain restaurant Zizzi where the pair dined at before falling ill. It was boarded off whilst investigators worked on the building and later found traces of the chemical weapon within it. AFP/Getty Skripal attack aftermath – in pictures Scene of attack Large areas of central Salisbury were cordoned off by police following the discovery of the Skripals. Traces of nerve agent were also found in The Mill pub. PA Skripal attack aftermath – in pictures Victim - Nick Bailey Detective Sergeant Nick Bailey, rushed to the aid of the Russian ex-spy and his daughter who were targeted with a nerve agent. He was hospitalized after aiding them and didn't leave until three weeks after the attack. Wiltshire Police/Rex Skripal attack aftermath – in pictures Police investigation - Skripal’s home Police believe they were poisoned at home, and detectives found the highest concentration of novichok on the front door of Mr Skripal’s house. Getty Skripal attack aftermath – in pictures Theresa May visits scene of attack Britain's Prime Minister Theresa May spokes with Wiltshire Police's Chief Constable Kier Pritchard near where the Skripal's were found. Britain expelled 23 Russian diplomats over the nerve agent poisoning and suspended high-level contacts, including for the World Cup on March 14. Theresa May told parliament that Russia had failed to respond to her demand for an explanation on how a Soviet-designed chemical, Novichok, was used in Salisbury. AFP/Getty Skripal attack aftermath – in pictures Skripal days before attack Sergei Skripal days before he was exposed to Novichok, that has left him fighting for life. ITV News Skripal attack aftermath – in pictures Police investigation - military involvement British soldiers were deployed soon after the attack to help a counter-terrorism investigation into the nerve agent attack. One of the places they were asked to help out with was Skripal's home and it's surrounding. They were asked to remove a vehicle connected to the agent attack in Salisbury, from a residential street in Gillingham. AFP/Getty Skripal attack aftermath – in pictures Police investigation Personnel in protective coveralls and breathing equipment cover an ambulance with a tarpaulin at the Salisbury District Hospital. AFP/Getty Skripal attack aftermath – in pictures Police investigation The investigation extended to the grave of Sergei Skripal's son Alexander in London Road cemetery. Getty Skripal attack aftermath – in pictures Police investigation The Counter Terrorism Policing Network requested assistance from the military to remove a number of vehicles and objects from Salisbury. EPA Skripal attack aftermath – in pictures Home Secretary visits scene of attack Home Secretary Amber Rudd visited the scene of the nerve agent attack at the Maltings shopping centre on 9 March. Getty Skripal attack aftermath – in pictures Yulia Skripal speaks for the first time Yulia Skripal, speaking for the first time, said she felt lucky to have survived the nerve agent attack in Salisbury which left her fighting for life. Ms Skripal said her life had been “turned upside down” by the assassination attempt. But the Russian national added she hoped to return to her homeland one day, despite the Kremlin being blamed for the attack. Reuters

Some in the Russian diplomatic hierarchy are also urging caution. A former senior diplomat, who recently left the country’s foreign service, said: “This would be a drastic step if this is what they are thinking. But one needs to be especially careful. Both Russian and British people involved in intelligence face common enemies in Islamist terrorists and will be in danger if both sides start identifying each other’s officers.

“The British have produced no evidence of their claims about this nerve agent attack. Boris is saying a lot, but he always does, and we know he is not really taken seriously by most European governments. And we hear the new British defence minister made a fool of himself the other day. So it is best if everyone tries to remain calm and not do anything too drastic.”