In that case, two men were identified as suspects but Russian Federation refused to hand them over.
Viktoria Skripal also said that she doubts that Sergei Skripal is still alive because he has not communicated with the family since the poisoning.
He said his partner, Dawn Sturgess, 44, had applied some of the substance to her wrists before feeling unwell.
He was hospitalized and his girlfriend Dawn Sturgess died after being exposed to the contents.
They entered the country carrying the Novichok in a modified perfume bottle, which United Kingdom authorities released a picture of in its September 4 statement.
Previously, during a search of Mr Rowley's home in Muggleton Road, Amesbury, on July 10, a small box labelled as Nina Ricci Premier Jour was recovered from a rubbish bag in the kitchen.
Below are excerpts from May's speech.
"We have ascertained exactly who was responsible and the methods they used", Fleming told the Billington Cyber Security Conference according to extracts released by his office.
British authorities and the global chemical weapons watchdog say the Skripals were exposed to Novichok, a type of military-grade nerve agent developed by the Soviet Union during the cold war.
What were their movements on the days leading up to the poisoning? They stayed in a hotel in London - where traces of Novichok were also found - and made two trips to Salisbury.
They spent weeks critically ill in hospital but have since been discharged.
The following day, the suspects undertook what police said was a reconnaissance mission, traveling by train to Salisbury from London.
Police said CCTV shows the two suspects in the vicinity of the property on that date.
Police say the two men flew back to Moscow from Heathrow Airport on the evening of March 4, hours after the Skripals were found collapsed on a park bench in Salisbury.
"The Russian state needs to explain what happened in Salisbury", May added.
For Russia, even though the assassination attempt failed, the Novichok operation could still be considered a success.
British prosecutors have charged the two men with the attack on the Skripals, but acknowledge that Russian Federation will not extradite them. Moscow strongly dismissed all speculations on that score, adding that programs for developing this substance had never existed in the Soviet Union or Russian Federation.
"Within the past decade Russian Federation has produced and stockpiled small quantities of these agents, long after it signed the Chemical Weapons Convention".
British Prime Minister Theresa May said in parliament on September 5, that the attack on Skripal was "not a rogue operation" and must have been approved "at a senior level of the Russian state", The Associated Press reported.
The suspects at Salisbury train station.
Security agencies could also seek the expulsion of foreign intelligence officers if their activity is deemed to be especially intrusive or threatens real damage to United Kingdom interests.
"Based on this work, I can today tell the House that, based on a body of intelligence, the Government has concluded that the two individuals named by the police and CPS are officers from the Russian military intelligence service, also known as the GRU".
"The GRU is a highly-disciplined organization with a well-established chain of command".
US President Donald Trump, German Chancellor Angela Merkel, French President Emmanuel Macron and Canadian PM Justin Trudeau earlier issued a joint statement with Theresa May agreeing with the British assessment that the operation was "almost certainly approved at a senior government level" in Moscow.
Where are the suspects now?
Sue Hemming of the Crown Prosecution Service said Britain would not ask Moscow to extradite the men because Russian law forbids extradition of the country's citizens.
"Of course, Russian Federation has repeatedly refused to allow its nationals to stand trial overseas, citing a bar on extradition in its constitution". We want to keep our journalism open and accessible and be able to keep providing you with news and analyses from the frontlines of Israel, the Middle East and the Jewish World.