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.

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. Speaking at a UN Security Council meeting that the Russians 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, 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 1900s, .

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.

Russian ambassador to the UK: 'we have a lot of suspicions about Britain'

"We can't give an advance approval to results of the investigation, in which we aren't taking part and which is kept secret," he said. "We would accept the results of any investigation that would be fair, not the one organised in a fraudulent way."

Earlier, Moscow's ambassador to London Alexander Yakovenko said Russia had never made novichok. He said the Kremlin would accept the results of OPCW tests but only if there was transparency and they were confirmed by experts from outside Europe and Nato.

British Ambassador Karen Pierce said before the Security Council meeting that she had "a bit of a fear" that Moscow is trying "to build a narrative" for rejecting the watchdog's findings.

Ms Pierce later told the Security Council that Britain's actions “stand up to any scrutiny” and pledged to keep the body updated on the inquiry. “We have nothing to hide ... but I do fear that Russia might have something to fear,” Ms Pierce added.

Deputy US Ambassador Kelley Currie put her support behind the British diplomat, saying it was the US's "firm belief that Russia is responsible for this chemical weapons attack on UK soil". The US sent home 60 Russian diplomats last week in a show of solidarity with the UK – the largest single expulsion of Russian diplomats in American history.

Countries join UK expelling Russian diplomats over spy poisoning Show all 24 1 /24 Countries join UK expelling Russian diplomats over spy poisoning Countries join UK expelling Russian diplomats over spy poisoning United States Donald Trump has expelled 60 Russian diplomats from the US and closed the consulate in response to the Sergei Skripal spy poisoning. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning Great Britain Prime Minister Theresa May confirmed Britain would be expelling 23 Russian diplomats. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning Ukraine Ukrainian president Petro Poroshenko has expelled 13 Russian diplomats. Getty Countries join UK expelling Russian diplomats over spy poisoning Germany Germany's Chancellor Angela Merkel has expelled 4 Russian diplomats. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning France France's President Emmanuel Macron has also expelled 4 Russian diplomats. Reuters Countries join UK expelling Russian diplomats over spy poisoning Poland Poland's President Andrzej Duda has expelled 4 Russian diplomats. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning Lithuania President of Lithuania Dalia Grybauskaite has expelled 3 Russian diplomats. Getty Countries join UK expelling Russian diplomats over spy poisoning Czech Republic Czech Republic President Milos Zeman has also expelled 3 Russian diplomats. AFP Countries join UK expelling Russian diplomats over spy poisoning Netherlands Netherlands Prime minister Mark Rutte has expelled 2 Russian diplomats. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning Latvia Prime Minister of Latvia Maris Kucinskis has expelled 1 Russian diplomat. Getty Countries join UK expelling Russian diplomats over spy poisoning Estonia Estonia's Prime Minister Juri Ratas has expelled 1 Russian diplomat. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning Croatia Croatia President Kolinda Grabar-Kitarovic has expelled 1 Russian diplomat. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning Italy Italian President Sergio Mattarella has expelled 2 Russian diplomats. Getty Countries join UK expelling Russian diplomats over spy poisoning Canada Canadian Prime Minister Justin Trudeau has expelled 4 Russian diplomats. Getty Countries join UK expelling Russian diplomats over spy poisoning Finland Finland's President Sauli Niinisto has expelled 1 Russian diplomat. Reuters Countries join UK expelling Russian diplomats over spy poisoning Denmark Danish Prime Minister Lars Lokke Rasmussen has expelled 2 Russian diplomats. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning Romania Romania's President Klaus Werner Iohannis has expelled 1 Russian diplomat. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning Norway Norwegian Prime Minister Erna Solberg has expelled 1 Russian diplomat. REUTERS Countries join UK expelling Russian diplomats over spy poisoning Spain Spanish Prime Minister Mariano Rajoy has expelled 2 Russian diplomats. Getty Countries join UK expelling Russian diplomats over spy poisoning Sweden Sweden's Prime Minister Stefan Lofven has expelled 1 Russian diplomat. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning Albania Albanian President Ilir Meta has expelled 2 Russian diplomats. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning Australia Australian Prime Minister Malcolm Turnbull has expelled 2 Russian diplomats. Getty Countries join UK expelling Russian diplomats over spy poisoning Macedonia Macedonia President Gjorge Ivanov has expelled 1 Russian diplomat. AFP/Getty Countries join UK expelling Russian diplomats over spy poisoning Hungary President of Hungary Janos Ader has expelled 1 Russian diplomat. AFP/Getty

While scientists at the Porton Down biological and chemical weapons laboratory near Salisbury have concluded the toxin was novichok, its chief executive said on Tuesday they had not yet determined whether it was made in Russia.

Britain says there is no plausible explanation other than that Russia was behind the attack. Foreign secretary Boris Johnson has accused Russia of running a disinformation campaign, with Mr Yakovenko suggesting Moscow wants its own answers from Britain.

“We have a lot of suspicions about Britain,” said Mr Yakovenko. “If you take the last 10 years, so many Russian citizens died here in the UK, under very strange circumstances ... My question is why is it happening here?”

Also on Thursday, Yulia Skripal released her first statement since the poisoning, saying she was disoriented from the attack but getting stronger every day. Her father remains in a coma.

In her statement through British police, Ms Skripal thanked hospital staff and people who came to her aid when “when my father and I were incapacitated”.

“I woke up over a week ago now and am glad to say my strength is growing daily. I am grateful for the interest in me and for the many messages of goodwill that I have received,” Ms Skripal, 33, said.

“I am sure you appreciate that the entire episode is somewhat disorientating, and I hope that you'll respect my privacy and that of my family during the period of my convalescence,” she added.

Hours before the statement, Russian state TV and Interfax news agency claimed that Ms Skripal had phoned her cousin Viktoria Skripal in Russia, saying she and her father were both recovering and that she expected to leave hospital soon.

“Everything is fine, everything is fixable, everyone is getting better, everyone is alive,” they quoted her as saying. Asked about her father's health, Ms Skripal was cited as saying: “Everything is fine, he is resting right now, sleeping ... Nobody has any problems that can't be put right.”

Russian state TV said it could not vouch for the authenticity of the quotes.

Russia is also said to be seeking consular access to the Skripals as they seek to defend themselves from the UK's allegations. Ms Pierce said the request had been conveyed to Ms Skripal, but the final decision would be up to her. A British Foreign Office spokesman had earlier said:

“We have conveyed to Ms Skripal the Russian Embassy's offer of consular assistance. Ms Skripal is now able to choose if and when to take up this offer, but to date she has not done so.”