Relations between the UK and Russia remain in a “deep-freeze” three years after a chemical weapons attack in Salisbury killed one and left a city shaken.

Sir David Lidington, who was former Conservative prime minister Theresa May’s de facto deputy at the time, said the Government needs to strengthen its commitment to the security services in the wake of the attack.

Sir David, the chairman of the foreign policy think tank Rusi, said: “Three years on, the UK’s relationship with Russia remains in deep freeze.

“It’s hard to see any real thaw happening while the Russian authorities reject any responsibility for the Salisbury attack and refuse to allow suspects to be questioned.

“Salisbury was a reminder of the serious threat posed by even a low-level chemical weapons attack.

“To confront that threat, the Government will need to maintain and strengthen its commitment to our security and intelligence services and redouble their efforts to ensure that the UK’s national security strategy brings together our domestic and our international capabilities.”

Salisbury incident
Dawn Sturgess, who died after being exposed to nerve agent Novichok (Metropolitan Police)

On March 4 2018, former Russian spy Sergei Skripal, 66, and his 33-year-old daughter Yulia were targeted with the nerve agent Novichok and left seriously ill.

Wiltshire Police Detective Sergeant Nick Bailey was also treated after coming into contact with the substance when he tried to help the pair.

Charlie Rowley and his partner Dawn Sturgess, 44, fell ill in nearby Amesbury months after the incident.

Ms Sturgess died in hospital in July after coming into contact with a perfume bottle believed to have been used in the attack on the Skripals and then discarded.

Earlier this month, Defence Secretary Ben Wallace warned of a growing threat of international chemical and biological attacks – with some regimes willing to use such weapons on their own people.

Last year, Russian opposition leader Alexei Navalny was, according to the German government, the victim of a Novichok poisoning too.