Russia's ambassador to the United Nations has warned British officials they are "playing with fire" and will be "sorry" over their response to the poisoning of a former double agent and his daughter in Salisbury, Independent reported.

Theresa May has said it was "highly likely" that Russia was behind the attack, with the UK and a number of Western allies expelling more than 150 diplomats in response. Moscow has said it will respond to such measures in kind and speaking at a UN Security Council meeting that the Russian's called over the poisoning, Ambassador Vasily Nebenzya called Ms May's allegations "horrific and unsubstantiated".

"Couldn't you come up with a better fake story?" he asked at a UN Security Council meeting, adding: "We have told our British colleagues that you're playing with fire and you'll be sorry."

Russia called the meeting after the country was locked out of an investigation of the Salisbury poisoning by the Organisation for the Prohibition of Chemical Weapons (OPCW). Britain called on the watchdog group to investigate after ex-spy Sergei Skripal and his daughter, Yulia, were poisoned last month. Officials said the nerve agent used in the attack was novichok, a class of nerve agents developed by the Soviet Union in the late 1990s.

Mr Nebenzya said the poison had been developed in many countries, "in spite of the obviously Russian name". He also accused Britain of attempting to "discredit and delegitimise" Russia. 

Russia had called for a joint investigation into the poisoning – a suggestion that the Hague-based OPCW ultimately voted down. Foreign minister Sergei Lavrov said Russia may not be able to accept the results of the investigation if it cannot participate.