19 March, 2018
Scientists from the Organisation for the Prohibition of Chemical Weapons are also due to arrive in London as part of the investigation.
Russia's President Vladimir Putin has dismissing British accusations of Russia's involvement in ex-spy Sergei Skripal's poisoning as "nonsense", adding that Moscow is ready to cooperate with London in the probe.
Britain is to target wealth linked to the Kremlin in response to the poisoning of a former spy, foreign minister Boris Johnson said Sunday ahead of a visit by worldwide chemical weapons experts.
Speaking on the BBC's Andrew Marr Show, the foreign secretary said Moscow has breached worldwide rules by investigating the ways that nerve agents can be used for assassination.
"It's complete drivel, rubbish, nonsense that somebody in Russian Federation would allow themselves to do such a thing ahead of elections and the World Cup", Putin told supporters Sunday after winning a fourth term as president.
Chizhov also appeared to suggest that Britain itself may have been the source of the chemical agent.
Johnson told the BBC that "we actually have evidence within the last 10 years that Russian Federation has not only been investigating the delivery of nerve agents for the purposes of assassination but has also been creating and stockpiling Novichok" - the type of nerve agent Britain says was used in the attack.
Johnson is expected to brief his European Union counterparts on the case at a meeting of foreign ministers and NATO Secretary General Jens Stoltenberg in Brussels on Monday. He said in an interview that the only laboratories known to have fine-tuned the process were in Russian Federation and parts of the former Soviet Union. Tests to independently verify the British findings are expected to take at least two weeks, Britain's Foreign Office said.
The identification of Novichok as the weapon has become the linchpin of the British case for Russia's culpability in the poisoning.More news: Syrian rebels in eastern Ghouta agree to evacuate imprisoned Nusra fighters
He told ITV's Peston on Sunday: "We support exactly what the prime minister said and we condemn Russian Federation for this, condemn them".
"And Porton Down, as we now all know, is the largest military facility in the United Kingdom that has been dealing with chemical weapons research - and it's actually only eight miles from Salisbury".
Asked whether he was saying that Porton Down was responsible, Chizhov replied: "I don't know".
British newspapers on Sunday said the government was looking to pass emergency legislation to make it easier to seize assets in Britain acquired with dirty Russian money.
On Russia's Porton Down suggestion, Johnson said, "It was not the the response of a country that really believes it's innocent, that really wants to engage in getting to the bottom of this matter".
The tit-for-tat may continue this week.
Western powers see the poisoning of the Skripals as the latest sign of increasingly aggressive Russian interference in foreign countries.
Experts will take samples and send them to "reputable global laboratories", Mr Johnson said.
Russia's ambassador in London, Alexander Yakovenko, called for "cooler heads", telling the Mail on Sunday that the dispute is "escalating dangerously and out of proportion".