The Russian whistleblower who exposed the country's secret chemical weapons programme has revealed the horrific torturous effect of the Novichok nerve agents on their victims.
Vil Mirzayanov described the use of the lethal toxins as a 'brazen' attack by Vladimir Putin, who 'thinks he can use everything to kill enemies'.
Mr Mirzayanov says a large dose of Novichok 'paralyses' victims before 'it causes convulsions, you can't breathe and after that you die'.
The exiled scientist shocked the world in 1992 when he revealed that promises by the Soviet Union to reduce its chemical weapon stockpiles were hollow.
He worked in the top-secret Moscow laboratory where a new generation of even more potent poisons was being perfected.
These gruesome chemical weapons, named 'Novichok' after the Russian for 'newcomer', were designed to be even more lethal than VX or sarin.
At the time, one former top Soviet military adviser described them as 'political weapons', adding: 'They have a powerful moral and psychological effect.'
Shockingly, they can be created from common, unrestricted and undetectable industrial and agricultural chemicals available worldwide.
As a result, weapons inspectors fear other rogue nations, including Syria and North Korea, could have their own lethal stockpiles of the powerful nerve agents.
Speaking from his home in New Jersey last night, Mr Mirzayanov, 83, described the top-secret laboratory as a 'criminal enterprise'.
'It's a brazen attack,' he said. 'Putin thinks he can use everything to kill enemies. They don't tolerate any opponents.
'They should be punished. It's an open demonstration of this Russian terrorism.
'The Russian government is telling people who are thinking about revealing more secrets that they can expect the same fate.'
Asked how the nerve agent works, he added: 'It's for paralysing people, it causes you convulsions and you can't breathe and after that you die. If you get enough of a dose of it.
'It's real torture, it's impossible to imagine. Even in low doses the pain can go on for weeks. You cannot imagine the horror, it's so bad.'
The Novichok family of nerve agents were secretly developed over two decades at a research facility 50 miles outside the Russian capital.
Many times more potent than other better known chemical weapons, Novichok agents can render gas masks and protective equipment useless.
Sometimes described as 'gases' they are in fact liquid, intended to be delivered as a fine spray.
A series of poisons, known as Novichok 5, 7, 8 and 9 to identify them, were produced amid conditions of complete secrecy.
They all kill the same way. By inhibiting enzymes that control nerve receptors in the brain.
One expert said victims simply 'forget to breathe'. A tiny drop, almost undetectable, placed on the skin or inhaled can cause death within minutes.
Describing his work, Mr Mirzayanov said: 'They were normal laboratories, they were not underground or anything. They were testing and developing.
'There were around 1,000 people working on this, it was a big deal. You have to test it on animals and after that you have to study the chemical properties... so many laboratories were involved.'
In 1987, one physicist at the laboratory was saved despite being exposed to the chemical when a ventilator stopped working. Witnesses described how he staggered out of the room, describing seeing bright hallucinations before collapsing and being rushed to hospital by the KGB. He was left with permanent injuries after being critically ill for ten days and unable to walk for six months.
Read more on dailymail.co.uk.