British Foreign Secretary Boris Johnson said Russia has been stockpiling the deadly nerve agent used to poison a Russian former double agent in England and has been investigating how such weapons can be used in assassinations.
Britain has said Russia used the Soviet-era nerve agent called Novichok to attack Sergei Skripal and his daughter Yulia in the first known offensive use of such a weapon on European soil since World War Two. Russia has denied any involvement.
“We actually have evidence within the last 10 years that Russia has not only been investigating the delivery of nerve agents for the purposes of assassination, but has also been creating and stockpiling Novichok,” Mr Johnson told the BBC.
The identification of Novichok as the weapon has become the central pillar of Britain’s case for Russia’s culpability in the poisoning. Britain and Russia have each expelled 23 diplomats over the attack as relations between the two countries reach a post-Cold War low.
Mr Skripal, a former colonel in Russian military intelligence who betrayed dozens of Russian agents to Britain, and his daughter are fighting for their lives after they were found collapsed on a bench in the city of Salisbury two weeks ago.
Putin calls accusation 'rubbish'
Russian President Vladimir Putin on Sunday rubbished claims that Russia was responsible.
"It's complete drivel, rubbish, nonsense that somebody in Russia would allow themselves to do such a thing ahead of elections and the World Cup," Mr Putin told supporters after winning a fourth term as president.
"We have destroyed all chemical weapons," he added.
Technical experts from Organisation for the Prohibition of Chemical Weapons will visit Britain on Monday to collect samples of the nerve agent used in the attack.
Russian President Vladimir Putin won a fourth term on Sunday. Source: AAP
"These will then be despatched to highly-reputable international laboratories selected by the OPCW for testing with results expected to take a minimum of two weeks," said a statement by Britain's Foreign Office.
Mr Putin said Russia is "ready to take part in the investigation", although earlier on Sunday Mr Johnson accused the Russians of "smug sarcasm and denial" in response to the accusations.
Moscow's "malign, disruptive behaviour" internationally was the reason why allies were "inclined not to give Russia the benefit of the doubt," he told BBC's Andrew Marr Show.
Mr Johnson also said Britain would target wealth linked to the Kremlin as a further measure following the spy poisoning.
"Where people have obtained wealth by corruption and where we can see a link with the Kremlin, with Vladimir Putin, it may be possible to have unexplained wealth orders and other sanctions on those individuals," Mr Johnson said.
Mr Johnson said the government was considering something similar to the US "Magnitsky Act" which was adopted in 2012 to punish Russian officials accused of human rights violations.
The act imposed a visa ban and froze the assets of Russian officials implicated in the death of lawyer Sergei Magnitsky, a tax fraud whistleblower who died in Russian custody in 2009.
However, the minister faced awkward questions over a tennis match he played with the wife of former Kremlin minister Vladimir Chernukhin, in return for a £160,000 ($289, 224) donation to his Conservative Party.
Russia points at Porton Down
On Saturday, Russia's ambassador to the European Union, Vladimir Chizhov, said Moscow "had nothing to do" with the attack, accusing Johnson of "acting in an inappropriate manner" by pointing the finger at Mr Putin.
"Russia has stopped production of any chemical agents back in 1992," he told Mr Marr, the day after Moscow expelled 23 British diplomats in a tit-for-tat measure.
But the Foreign Office dismissed the claim, saying it had "information indicating that within the last decade, Russia has investigated ways of delivering nerve agents likely for assassination.
"And part of this programme has involved producing and stockpiling quantities of Novichok," a statement said.
Mr Chizhov also appeared to suggest that Britain itself may have been the source of the chemical agent.
"When you have a nerve agent, you check it against certain samples you have in your laboratories," he said.
"And Porton Down, as we now all know, is the largest military facility in the UK that has been dealing with chemical weapons research - and it's actually only eight miles from Salisbury."
Mr Johnson called the accusation "satirical", adding it was "not the response of a country that really believes itself it to be innocent."
