Russia’s foreign minister has claimed Sergei and Yulia Skripal were not poisoned by nerve agent novichok, but a separate chemical possessed by the UK and US.

Sergei Lavrov said Moscow had received information from a laboratory in Spiez, Switzerland suggesting the Russian double agent and his daughter were exposed to a non-lethal substance known as BZ.

He claimed the laboratory had passed Russia confidential information after analysing samples of the agent used in the attack on the Skripals in Salisbury last month.

Mr Lavrov said the toxin was not produced in Russia, but was in service in Britain, the United States and other Nato nations, Russian state media reported.

"Based on the results of the examination, traces of the toxic chemical BZ and its precursors, related to chemical weapons of the second category in accordance with the Convention on the Prohibition of Chemical Weapons, were found in the samples,” Mr Lavrov said, according to state-owned Sputnik News.

“BZ is a nerve agent temporarily disabling a person. The effect is achieved within 30-50 minutes and lasts up to four days."

Mr Lavrov noted the Organisation for Prohibition of Chemical Weapons (OPCW) had mentioned neither novichok, nor BZ in its independent report into the poisoning.

However, the OPCW did say its scientists had “confirmed the findings of the United Kingdom relating to the identity of the toxic chemical”.

Mr Lavrov nonetheless insisted: “If, of course, the OPCW refutes the fact of using the laboratory of Spiez, it will be interesting to listen to its explanations."

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

Britain has accused Russia of carrying out an attempted assassination of Mr Skripal, an allegation Moscow has routinely denied.

He was found unconscious with his 33-year-old daughter on a park bench on 4 March, with medical staff later determining they had been exposes to a nerve agent.

Ms Skripal is recovering from the attack at a secure location after being discharged from hospital on Monday. Mr Skripal remains seriously ill in hospital, although his condition is longer thought to be critical.