Police activity outside a block of flats on Muggleton Road in Amesbury, Wiltshire, where a couple were poisoned with a nerve agent

Police are still hunting for an item contaminated with a Soviet-era nerve agent blamed for the collapse of a couple in Amesbury after the UK government accused Russia of using ”barbaric and inhumane” chemical weapons on Britain’s streets.

Home secretary Savid Javid chaired an emergency Cobra meeting after Dawn Sturgess and Charlie Rowley fell critically ill in Amesbury four months after exposure to the same novichok toxin used in an assassination attempt on Russian ex-spy Sergei Skripal and his daughter.

The couple are fighting for life in hospital after falling ill on Saturday.

Mr Javid told MPs that results from the government’s Porton Down laboratory confirmed the pair had been poisoned with ”the exact same nerve agent” used in March’s assassination attempt, which the British government alleges was planned by the Kremlin.

Mr Rowley, 45, and Ms Sturgess, 44, are not thought to have been deliberately targeted and have no known links to the Skripals or espionage.

One theory understood to be under investigation is that the pair may have inadvertently found a container used to transport the nerve agent for the initial attack and which may have been discarded in a public place.

Their poisoning has raised serious questions about the multi-million-pound clean-up following the attack in Salisbury, about eight miles from Amesbury.

Police said there is no evidence that either of the latest victims had recently visited any of the sites that were part of the original clean-up.

Securities minister Ben Wallace said the public are at “low risk” but “not zero risk”.

The Russian government has denied involvement in the attack on the Skripals and any role in or knowledge of the incident in Amesbury.