Britain's national security adviser accuses Russian of testing chemical agents on door handles before the Salisbury attack
UK: Russia spied on ex-double agent Sergei Skripal for years
Russia's intelligence agencies spied on former double agent Sergei Skripal and his daughter Yulia for at least five years before they were poisoned with a nerve agent in March, the national security adviser to Britain's prime minister said.
Email accounts of Yulia had been targeted in 2013 by cyber specialists from Russia's GRU military intelligence service, Mark Sedwill said in a letter to NATO Secretary General Jens Stoltenberg on Friday.
It was "highly likely that the Russian intelligence services view at least some of its defectors as legitimate targets for assassination", Mr Sedwill said in the letter.
Mr Sedwill - who published the letter on Twitter on Friday - also said that Russia has tested means of delivering chemical agents "including by application to door handles", pointing out that the highest concentration of the chemical found after the attack was on Skripal's front door handle.
He said Russia had "the technical means, operational experience and motive for the attack on the Skripals and that it is highly likely that the Russian state was responsible".
The UK's national security adviser said "credible open-source reporting and intelligence" showed that in the 1980s the Soviet Union developed a family of nerve agents known as Novichoks at a base in Shikhany near Volgograd.
"The codeword for the offensive chemical weapons programme (of which Novichoks were one part) was FOLIANT... It is highly likely that Novichoks were developed to prevent detection by the West and to circumvent international chemical weapons controls," he said.
In the 2000s, Mr Sedwill said Russia had trained military personnel in using these weapons, including on door handles.
The Skripals were targeted by a nerve agent attack that left both of them critically ill for weeks. They were found slumped on a bench in the English city of Salisbury on March 4.
British Prime Minister Theresa May has said it is highly likely that Moscow was behind the attack although Moscow denies any involvement.
Russian Foreign Minister Sergei Lavrov noted on Friday that a report this week by the Organisation for the Prohibition of Chemical Weapons did not confirm the origin of the poison used against the Skripals.
Mr Lavrov said the report only confirmed the composition of the substance and that Britain's claim that it confirmed the UK position on the Skripal case was overstated.
Separately on Friday, Russia's ambassador to Britain said he was concerned the British government was trying to get rid of evidence related to the case.
"We get the impression that the British government is deliberately pursuing the policy of destroying all possible evidence, classifying all remaining materials and making an independent and transparent investigation impossible," Alexander Yakovenko told reporters in London.
He also said Russia could not be sure about the authenticity of a statement issued by Yulia Skripal on Wednesday in which she declined the offer of help from the Russian embassy.
“The British government still hasn’t produced any evidence in support of its position that would confirm their official version,” he told a press conference.
“We get the impression the British government is deliberately pursuing the policy of destroying all possible evidence.”
Late Friday, the Russian embassy in the UK released its "classified" report on Salisbury, outlining what it considers to be the "crucial elements" of British and Russian positions on Salisbury.