The West’s knowledge of the novichok nerve agent used to poison a former Russian spy and his daughter came from a sample smuggled to Germany in the 1990s, local media reports.

Britain blamed Russia for the attack on Sergei Skripal and his daughter, Yulia, and the Organisation for the Prohibition of Chemical Weapons confirmed its analysis.

More than 20 Western countries expelled Russian diplomats over the issue, in the biggest expulsion since the Cold War.

In a joint report, German newspaper Sueddeutsche Zeitung, the weekly Die Zeit and broadcasters NDR and WDR said Germany’s BND spy agency had secured the sample of novichok from a Russian scientist.

The sample was taken to Sweden for analysis and the chemical formula given to the German government and military, the report said, citing sources.

Western countries used the information to help develop countermeasures.

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

The story could help explain how Britain was able to analyse the poison it said was used to attack the Skripals in Salisbury in March.

Moscow has denied blame for the attack and accused London of not being forthcoming in how it investigated the poisoning.

“The finding about a class of weapons known as novichok developed in the former Soviet Union largely stems from a previously unknown secret operation of the BND,” a summary of the German news organisations’ joint report said.

It said it was unclear what had become of the sample, and said the Swedish government had said it could not provide information about the process on short notice. The BND also declined to comment on the report.

A spokesman for the German defence ministry said the military researched how to protect against chemical, biological, radioactive and nuclear weapons materials, in accordance with international law, but could not provide details so as to safeguard members of the military and the German population.

“This includes the question about which substances are being researched and the availability of these materials,” a ministry spokesman said. “As a result, statements and assertions about this are not confirmed, denied or commented on.”

The German media report said the BND had informed the US and British intelligence agencies about the case following the analysis, and small amounts of the poison were later produced in several Nato member states to test Western protective gear, testing equipment and antidotes.

Mr Skripal remains in hospital in Salisbury, where his condition is said to be improving and he is no longer in a critical condition.

His daughter was discharged last month and is recovering at an undisclosed location.