Speaking to Sky News on Tuesday, Gary Aitkenhead, chief executive of Porton Down laboratory said the poisonous substance used to carry out the attack was the military-grade nerve agent Novichok but said scientists did not identify where it was manufactured.
The British government insisted that several pieces of information contributed to its conclusion that the Russian government was responsible for the nerve agent attack, including intelligence that Russia had produced Novichok within the last decade and had investigated ways of delivering nerve agents for assassinations.
A spokesperson said: "We have been clear from the very beginning that our world leading experts at Porton Down identified the substance used in Salisbury as a Novichok, a military grade nerve agent".
"It's a military grade nerve agent which requires extremely sophisticated methods in order to create - something that's probably only within the capabilities of a state actor".
A United Kingdom government spokesperson on Tuesday reiterated Britain's assertion that Russian Federation was responsible for the nerve agent attack, saying that the Porton Down lab's research is "only one part of the intelligence picture".
Many countries have expelled Russian diplomats from there countries and Russia has retaliated by expelling 60 US diplomats and closing the USA consulate in St. Petersburg, Russia.
The admission is likely to be seized on by Russian Federation which has suggested that the nerve agent could have come from other nations, or from Porton Down, which is eight miles from Salisbury, the scene of the attack.
The official did not divulge those details, but said Russian involvement in the attack is the only "plausible explanation".
"Not the Salisbury poisoning but all the actions".
Britain blames Russian Federation for the pair's poisoning with a Soviet-developed nerve agent.
The global chemical weapons watchdog agency has said it will meet Wednesday to discuss Britain's USA -backed allegation that Russian Federation is responsible for the poisoning of a former double agent in England.
The OPCW (Organisation for the Prohibition of Chemical Weapons) said its executive council would meet in the morning in The Hague. British officials say his 33-year-old daughter's health is improving.
Russian President Vladimir Putin says Moscow wants a thorough probe into the poisoning of an ex-Russian spy in Britain and will demand to be part of it. British authorities suspect Skripal was poisoned by a Soviet-made nerve agent.
Skripal, 66, a former Russian intelligence agent convicted of spying for Britain, remains in critical condition.
Britain has blamed Russian Federation for the March 4 nerve agent attack, sparking a series of tit-for-tat explusions of diplomats by Britain and its allies as well as Moscow.
The fallout from the Salisbury attack could become "worse" than the cold war, retired Russian Federation general Evgeny Buzhinsky has claimed.
Worse than the Cold War is a real war.
WASHINGTON: expelled 60 USA diplomats on Thursday and announced it would eject scores from other countries that have joined London and Washington in censuring Moscow over the poisoning of a spy.