Russian Foreign Ministry spokesman Maria Zakharova denied that Russia or the Soviet Union had ever developed novichok, the class of nerve agent that Britain says was used to poison the Skripals.
He told BBC One's The Andrew Marr Show: "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".
Russian Federation denies involvement and warned for days that it would respond to the U.K.'s expulsion of 40 percent of its diplomats in London.
"They will then be testing them in global. internationally reputable laboratories", Boris Johnson told reporters.
"Their response has been a mix of smug sarcasm and denial and obfuscation", he said.
Experts from the Organisation for the Prohibition of Chemical Weapons (OPCW) will arrive in the United Kingdom on Monday to test samples of the chemical.
The Foreign Office said there was "not an ounce of truth" in Mr Chizhov's suggestion of a link to Porton Down.
Russia's ambassador to the EU, Vladimir Chizhov, prompted a strong response when he suggested the poison may have come from the Porton Down laboratory, which is around eight miles from Salisbury.
He said Russian Federation did not stockpile the poison and that the Porton Down lab was only eight miles (12km) from the city.
Moscow's "malign, disruptive behaviour" internationally was the reason why allies were "inclined not to give Russian Federation the benefit of the doubt", he added.
Johnson said it was "not the response of a country that really believed itself to be innocent".
Russia's response is more robust than expected. "We can be reassured by the strong support we have received from our friends and allies around the world", May said.
The Foreign Secretary said only Russians would suffer due to Moscow's expulsion of 23 British diplomats and the closure of the British Council.
Russian Federation also says it is shutting down the activities of the British Council, which fosters cultural links between the two countries.
Energy firms have been warned to prepare for blackouts as fears grow of a Russian cyberattack on the United Kingdom if the row continues.
He called for restraint and "cooler heads", telling the Mail on Sunday: "This dispute is indeed escalating dangerously and out of proportion".
He said: "Government has seized the opportunity to present itself as robust and competent to the public opinion".
On Monday, British Prime Minister Theresa May confronted Moscow with an ultimatum to reveal the details of the alleged Skripal plot.
And in its latest attempt to mock the attack, the embassy tweeted today: "In absence of evidence, we definitely need Poirot in Salisbury!" It left former spy Sergei Skripal and his daughter Yiulia fighting for their lives in hospital.
Alexei Navalny claimed last night that kicking Kremlin spies out of London would only help the Russian president. "The campaign that Britain has fomented with the World Cup soccer tournament, which instead of England will take place this year in Russian Federation, always leads to certain suspicions".
Mr Navalny told the Sunday Times: "It's about their families".
The opposition leader singled out well-known figures such as Chelsea's owner Roman Abramovich and Alisher Usmanov, who has a stake in Arsenal.
Mr Johnson said: "He let down his party and country by seemingly aiding the efforts of the Russian propaganda machine by casting doubt over what is obvious to any objective onlooker".
"If their assets were frozen, if their children could no longer study in Britain, they would begin to see Putin as a liability and that would be a problem for him".