The UK believes it is highly likely that the Russian State orchestrated the attack
Britain’s national security adviser has claimed that Russian intelligence has been spying on the family of former agent Sergei Skripal for at least five years.
UK security chief Mark Sedwill said cyber experts from Russia’s GRU military intelligence agency targeted email accounts held by Mr Skripal’s daughter Yulia as far back as 2013.
He said a programme set up in Russia in the 2000s trained personnel from "special units" in the use of chemical warfare agents - including investigating how nerve agents could be administered through door handles.
In an analysis of samples taken from the home of the Skripals, the highest concentrations of toxic chemical novichok, thought to be responsible for their poisoning, was found on door handles.
Nearly a month after the pair were found unconscious on a bench in Salisbury, Yulia has been discharged from hospital and her father Sergei is no longer in a critical condition.
Yulia has also turned down an offer of assistance from the Russian Embassy.
Mr Sedwill made the claims in a letter to NATO secretary general Jens Stoltenberg.
Yesterday, the Russian Embassy published an 8,000-word report into the Skripal poisoning row.
Our report "Salisbury: a Classified Case" seeks to summarize the sequence of events as well as to present crucial elements of Britain’s and Russia’s position. For the first time, UK replies to Russian questions are revealed in full. Read the report: https://t.co/akllGbDhrq pic.twitter.com/yrKYRj7qMK— Russian Embassy, UK (@RussianEmbassy) April 13, 2018
The report again insisted that Moscow had "nothing to do" with the Salisbury attack, and accused the UK of the "forcible detention or imprisonment" of the ex-Russian spy and his daughter.
At a press conference arranged before the release of Mr Sedwell’s letter, the Russian ambassador to the UK Alexander Yakovenko said he had not been made familiar with the allegations detailed in it.
"If somebody was spying, why were the British services not complaining about that?” he asked.
"We didn't hear any signs, any applications from the British side."
Russia has continued to deny any involvement in the poisoning of the former spy and his daughter, asking for further investigation into what Mr sedwell describes as an "attack."
Thursday's note, which gave evidence for the UK belief Russia was responsible for poisoning the Skripals, followed a report by the Organisation for the Prohibition for Chemical Weapons.
The OPCW announcement confirmed that "high purity" novichok was used in Salisbury, however it offered no opinion on where the substance was manufactured – or who was behind the attack.
The UK believes it is highly likely that the Russian State orchestrated the attack.
However the country’s chemical weapons research facility has admitted that, while it can confirm novichok was the substance used, it cannot tell where it was manufactured.
Novichok is a military-grade nerve agent developed by Russia from the 1970s onward, however the country’s president Vladimir Putin has warned that it could be produced in up to 20 countries.
UK Foreign Secretary Boris Johnson called the results "conclusive," despite the fact the OPCW offered no opinion on who carried out the attack.
"There can be no doubt what was used and there remains no alternative explanation about who was responsible - only Russia has the means, motive and record," he said.
He has previously come under fire for claiming that British researchers were "absolutely categorical" that there was "no doubt" the source of the nerve agent was Russia – despite the lack of assurance from UK scientists.
In his letter, Mr Sedwill backed his Mr Johnsons claims, adding that Russia had "produced and stockpiled small quantities of novichoks" under the training programme on chemical weapons in the 2000s.