Russia spied on Sergei Skirpal and his daughter for at least five years, says UK

National Security Adviser says Russia had investigated applying nerve agents to door handles – the method used in Salisbury

Russia has been spying on Sergei and Yulia Skripal for at least five years and investigated how to launch nerve agent attacks using door handles, Britain has said.

In a letter to Nato, national security adviser Sir Mark Sedwill revealed that they were the subject of “interest” from the Kremlin’s security services since 2013.

He said email accounts belonging to Ms Skripal had been targeted by cyber specialists with Russia’s GRU intelligence agency, where her father was a colonel while passing secrets to Britain as a double agent.

Sir Mark said that even after being convicted of espionage and handed over in a high-profile spy swap, Mr Skripal may still have been seen as a target.

“It is highly likely that the Russian intelligence services view at least some of its defectors as legitimate targets for assassination,” he added.

“We continue to judge that only Russia has 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. There is no plausible alternative explanation.”

An independent investigation by the Organisation for the Prohibition of Chemical Weapons (OPCW) confirmed that a class of nerve agents known as novichoks were used in the assassination attempt.

Police said the substance was put on the front door of Mr Skripal’s home in Salisbury, poisoning him and his daughter on 4 March, along with one of the first police officers to respond.

Sir Mark said Russia investigated the delivery of nerve agents using door handles in a chemical weapons programme started in the 2000s, when special units were allegedly trained to apply the chemicals.

“Within the last decade, Russia has produced and stockpiled small quantities of novichoks under the same programme,” he added.

The OPCW said it had verified the UK’s analysis of the agent used but did not ascribe responsibility, sending the name and structure of the chemical to nations including Russia in a classified report.

It noted that the substance used was of “high purity” – a characteristic claimed by the British government to point to state involvement.

Sir Mark said the former Soviet Union developed novichok nerve agents primarily at the State Institute for Organic Chemistry and Technology at Shikhany, as part of a wider programme codenamed “Foliant”.

“It is highly likely that novichoks were developed to prevent detection by the West and to circumvent international chemical weapons controls,” he added. “The Russian state has previously produced novichoks, and would still be capable of doing so.”

Vladimir Putin’s government has repeatedly denied any involvement in the Salisbury attack, or breaking the Chemical Weapons Convention, and says all its stockpiles were destroyed.

But Sir Mark told Nato Secretary General Jens Stoltenberg that Russia’s chemical weapons programme continued after the collapse of the Soviet Union, and novichoks were being used by the military by the time it signed the convention in 1993.

He accused Russia of failing to report its work on novichoks at the time and continuing to develop the weapons after ratifying the convention, alleging that Vladimir Putin himself was involved in the programme in the mid-2000s.

“It is highly unlikely that any former Soviet republic other than Russia pursued an offensive chemical weapons programme after independence,” the letter concluded.

“It is unlikely that novichoks could be made and deployed by non-state actors such as a criminal or terrorist group, especially at the level of purity confirmed by OPCW.”

Citing the radioactive poisoning of Alexander Litvinenko, Sir Mark said Russia had a “proven record of conducting state-sponsored assassination”.

A public inquiry led by judge Sir Robert Owen, which concluded in 2016, said Russia had previously been involved in the assassination of its opponents using poisons.

The UK has called a meeting of the OPCW’s executive council on Wednesday, which will include several Nato members.

“I know that Nato will remain seized of the need to confront the increasingly aggressive pattern of Russia behaviour of which the attack in Salisbury was an acute and recent example,” Sir Mark said.

Ms Skripal, 33, is recovering in a secret location after being discharged from hospital, where her father remains seriously ill.

In a statement, she confirmed she had rejected a “kind” offer of consular assistance from the Russian embassy for the time being.

Tensions between Russia and the UK have worsened further over an alleged chemical attack in Syria (Syrian Civil Defence White Helmets via AP) (Syrian Civil Defense White Helmets via AP)

“I want to stress that no one speaks for me, or for my father, but ourselves,” Ms Skripal said.

“I am still suffering with the effects of the nerve agent used against us. I find myself in a totally different life than the ordinary one I left just over a month ago, and I am seeking to come to terms with my prospects, whilst also recovering from this attack on me.”

In a press conference at the Russian embassy in London, Ambassador Alexander Yakovenko expressed doubt over the authenticity of her statement.

“We didn’t produce novichok, we didn’t store this novichok, so-called under the Western classification, and it was never in our military forces,” he said.

“The investigation was conducted in the most non-transparent way ... we are not allowed to see our citizens, talk to doctors, have no idea about the treatment the Russian nationals receive.

“We cannot be sure that Yulia’s refusal to see us is genuine. We have every reason to see such actions as the abduction of two Russian nationals.”

The Russian embassy later published its own “report” into the attack, entitled “Salisbury: A Classified Case”, that repeated the denials and contained no significant new information.

Tensions between the UK and Russia have been heightened further by an alleged chemical attack by its Syrian allies on the rebel stronghold of Douma.

The US and France have threatened military action against President Bashar al-Assad’s forces, who are being backed by Russian air strikes, and cabinet ministers agreed last night on the “need to take action” against further violations.