Update 12.20pm: The fallout from the Salisbury poisoning could lead to the "last war in the history of mankind", a retired Russian general has warned.
Relations between Russia and the West could become "worse" than the Cold War and "end up in a very, very bad outcome" following the nerve agent attack, Lieutenant-General Evgeny Buzhinsky said.
Responding to arguments that many countries across the world believed the Kremlin was responsible for last month's attack, Mr Buzhinsky, who now heads an international security think tank the PIR Center, told BBC Radio 4's Today programme: "Please, when you say the world, you mean EU and United States and some other countries ... you see it's a cold war, it's worse than the Cold War because if the situation will develop in the way this (is) now, I'm afraid that it will end up in a very, very bad outcome."
Asked to spell out what this would mean, he said: "A real war, worse than a cold war is a real war, it will be the last war in the history of mankind."
He added: "You're saying that the pressure will continue, what are you going achieve? If you are going to achieve (the) regime change, it's useless, you don't know Russians. The more external pressure (there) is, the more the society is consolidated around the President."
Explaining how the situation could escalate, Mr Buzhinksy accused the West of "cornering" Russia which he argued was a "very dangerous thing".
He said: "You don't want to discuss, you say Russia should change its behaviour, it's not the kind of talk, it's not the kind of compromise we need.
"OK, you expel diplomats, we expel diplomats, you further expel, what's the next step, the breach of the diplomatic relations ... After that, I said that it may lead to nowhere. Actually, you are cornering Russia and to corner, Russia is a very dangerous thing."
Asked about other countries not believing the Kremlin's comments about the Salisbury poisoning, Mr Buzhinksy branded it "such a nonsense", arguing that in this crime Russian President Vladimir Putin "is the last guy to benefit".
Russia's foreign minister accused Britain and the US of spreading "lies and disinformation" about the poisoning of a Russian ex-spy in England, declaring that East-West tensions are worse now than during the Cold War.
Britain has blamed Russia for the March 4 nerve agent attack on former double agent Sergei Skripal and his daughter, Yulia.
Britain and two dozen of its allies have since expelled over 150 Russian diplomats. Moscow, which vehemently denies any involvement, has responded tit-for-tat.
Russian Foreign Minister Sergey Lavrov denounced the British accusations on Monday as a "mad and horrible provocation".
He argued that Russia had no motive to attack Mr Skripal, who was released in a 2010 spy swap from a Russian prison where he was serving time for spying for Britain.
"If there were any gripes against the man, he wouldn't have been swapped," Mr Lavrov said.
Russia's top diplomat also mocked Britain's claim that there was no plausible alternative explanation for the poisonings of the Skripals.
British intelligence agencies could have been involved and the case helped distract public attention from the British government's difficult talks to exit the European Union, Mr Lavrov said.
"There are other explanations besides those put forward by our Western colleagues, who declare that it can only be the Russians who are responsible," Mr Lavrov said. "It could also be advantageous to the British government, who clearly find themselves in a difficult situation having failed to fulfil their promises to voters over Brexit."
British officials have previously rejected similar Russian allegations.
Mr Lavrov said that Russia has called a meeting of the international chemical weapons watchdog for Wednesday to discuss the case and asked it to provide details of its cooperation with Britain in the poisoning probe.
Alexander Shulgin, the Russian representative at the Organisation for the Prohibition of Chemical Weapons (OPCW), said on Monday in televised remarks that the organisation must conduct an "open, thorough and unbiased investigation" with Russian experts' participation.
British authorities invited OPCW experts to take chemical samples from Salisbury, the English city where the father and daughter were sickened, and to analyse them.
Mr Shulgin warned that Moscow would not accept the agency's conclusions unless Russian experts are allowed to take part in the process.
Mr Lavrov also assailed the British authorities for stonewalling Russia's request for consular access to Yulia Skripal, 33, a Russian citizen whose condition has improved since she and her father fell critically ill on March 4.
"Many say that the situation now is worse than it was during the Cold War because some rules existed and decorum was observed back then," he said.
"Now, Britain, the US and a few countries blindly following them have dropped all decorum and engaged in blatant lies and disinformation."