The Russian foreign minister has suggested Britain may have poisoned its former agent Sergei Skripal, as the Kremlin continues to deny involvement.

Sergei Lavrov told a press conference there were “other explanations” over who may have targeted the former Russian double agent in Salisbury.

“Experts tell us that it may well be beneficial to the British special services, who are known for their ability to act with license to kill,” he said.

“[The nerve agent attack] could be beneficial to the British government, which has found itself in a difficult situation, unable to fulfil promises they made about Brexit.”

The UK accused Vladimir Putin's government of culpability after identifying the nerve agent used as Soviet-developed novichok.

Theresa May said Russia had failed to explain how it could have lost control of the weapon, meaning it must have been involved in the attack itself – an accusation the Kremlin denies.

Conspiracy theories blaming the UK have been circulating online since news first emerged of the attack on Mr Skripal and his daughter Yulia on 4 March.

Salisbury nerve agent attack: Sergei Skripal and daughter were poisoned with novichok on their front door

They have been amplified by Russian state media outlets, including the English language website Sputnik, which ran an editorial four days later arguing that “given their inveterate anti-Russian agenda, the British authorities have much more vested interest in seeing Skripal poisoned than the Kremlin ever would”.

Commentators have suggested supposed motives of the “false flag” attack including smearing Russia, damaging Vladimir Putin ahead of last month’s election or even to distract from a grooming scandal in Telford.

Supporters of the theory rely on the unsubstantiated assertion that Britain or its allies synthesised novichoks themselves following the fall of the Soviet Union, although some Russian officials have denied the weapon was ever created.

"Has the substance identified by British representatives as 'novichok' or analogous substances been researched, developed or produced in the UK?" asked the Russian Embassy's official Twitter account on Monday.

Ben Nimmo, of the Atlantic Council’s Digital Forensic Research Lab, said many Russian news articles furthering the claims were based on “interviews with former security chiefs and weird commentators” with no expertise or credibility.

He told The Independent a mounting disinformation campaign was using the “same techniques” as those seen after incidents including the downing of Malaysia Airlines flight 17 using a missile from Russia.

“You can think of them as dismiss, distort, distract and dismay,” Mr Nimmo said, saying conspiracies were part of distraction techniques.

The Kremlin has reacted angrily to the expulsion of Russian diplomats by Britain and its allies, starting tit-for-tat expulsions.

"It’s too obvious that out British colleagues are playing a game – we will insist on clarifying all facts and establishing the truth,” Mr Lavrov said.

"Our western partners have forgotten about good manners and have resorted to outright lies and misinformation.”

Responding to Mr Lavrov's suggestion that the attack may have been in the UK's interests, Jeremy Corbyn condemned the "appalling, illegal, criminal act".

"The identity of the poison has been traced back to that of Russian manufacture," the Labour leader told Channel 4 News.

"I suggest to Mr Lavrov, perhaps he should just hold on a minute. The investigation is being undertaken and it will identify, I hope, where it came from and who did it."

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

Independent investigators from the Organisation for the Prohibition of Chemical Weapons (OPCW) are working to verify the UK’s analysis of the substance used against Mr Skripal and his daughter.

They both remain in hospital, where the 66-year-old former spy remains in a critical condition. Ms Skripal has regained consciousness and is “improving rapidly”.

Mr Lavrov said it was "outrageous" that Britain had failed to give Russian officials access to the 33-year-old since news of her condition emerged.

Expressing hope that Mr Skripal, who is a British citizen, would recover in the same way as his daughter, he added: "I consider this is outrageous that so far our multiple requests demanding access to our citizens have been rejected or have remained unanswered."

Mr Skripal moved to Salisbury after being handed over in a Cold War-style spy swap in 2010, having been jailed for treason in Russia for allegedly passing secrets to MI6 while a colonel in the GRU military intelligence agency.

Experts at the Defence, Science and Technology Laboratory at Porton Down identified the nerve agent used against the Skripals as part of the Soviet-developed “novichoks” group.

Traces have been found at various sites visited by the pair in Salisbury, investigators said, but at “lower concentrations to that found at the home address”, where police believe it was placed on the front door.

The Russian foreign ministry has submitted a list of questions to the OPCW about its investigation, including what sort of assistance Britain had requested and how samples were taken.

It claimed it would cooperate with the OPCW’s investigations, but attacked the organisation just months ago after it found Russia’s ally Bashar al-Assad had used sarin in rebel-held areas in Syria.

Foreign ministry officials called an OPCW report biased, “unprofessional and amateur” at the time, claiming that civilian deaths in Khan Sheikhoun may have been “staged”.

Russia blocked UN Security Council action against the Syrian regime, then proposed changing the rules for inspectors at the Hague-based watchdog in ways that Western diplomats said would undermine its work.

The latest request came on the same day that 60 Russian diplomats and their families returned to Moscow on two planes after being expelled from the US. The step was also taken by more than 20 other countries, and Nato.