EVEN as President Vladimir Putin was winning his expected landslide victory in the Russian general election, Foreign Secretary Boris Johnson claimed that the country under Putin had been breaking international law for 10 years.

In the latest episode of the war of words that has followed the attempted murder by Novichok nerve agent in Salisbury of former spy Sergei Skripal and his daughter Yulia – as well as the injuries to police officer Detective Nick Bailey and the murder of Russian businessman Nikola Glushkov in London – Johnson has made his most serious accusation yet.

Johnson had already implicated Putin in the attack but went much further yesterday and accused Russia of creating and stockpiling chemical weapons which are banned under international law and which were supposed to have been destroyed.

READ MORE: Putin is only a threat to the West is we turn him into one

Johnson told the BBC’s Andrew Marr Show: “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.”

He added that Russia’s reaction to the incident “was not the response of a country that really believes itself to be innocent”.

Johnson also dismissed out of hand a suggestion by Russia’s EU ambassador Vladimir Chizhov that the Novichok might have come from the Porton Down laboratory in Wiltshire.

The Russians continue to deny any involvement in the poisoning. Russian foreign ministry spokeswoman Maria Zakharova said the UK was one of the most likely sources of the nerve agent, along with the Czech Republic, Slovakia, Sweden or possibly the United States.

He said a large number of former Soviet scientists had gone to live in the West, “taking with them the technologies that they were working on”.

In another political intervention Labour shadow chancellor John McDonnell said on Peston on Sunday that he agreed with Prime Minister Theresa May that Vladimir Putin was responsible: “Whichever way you look at it, he is responsible and all the evidence points to him.

“We support exactly what the Prime Minister said and we condemn Russia for this, condemn them.”

Experts from the Organisation for the Prohibition of Chemical Weapons will arrive in the UK today to test samples of the chemical.

In further developments intelligence sources have told America’s ABC News said that intelligence officials “now have a clearer picture of just how the attack was conducted”.

READ MORE: Alex Salmond gives support to Jeremy Corbyn over Salisbury probe

They report that is was used in a “dust-like powdered form” and was circulated through the vents of Colonel Skripal’s BMW.

Chemist Vil Mirzayanov, who revealed the existence of Novichok in the 1990s and later defected to the United States, said he was convinced Russia was behind the attack.

He told the BBC: “Russia is the country that invented it, has the experience, turned it into a weapon. This is the country that has fully mastered the cycle.”

On Saturday, the Russian foreign ministry made its tit-for-tat declaration to expel 23 Russian diplomats.

The British Council in Russia, which promotes cultural ties between the nations, will also close as will the British Consulate in St Petersburg.

Putin sails on regardless and now has another six years as president. The Russian state exit poll gave him 73.9 per cent of the vote, easily defeating his closest competitor and up from the 64 per cent tally in 2012.

However the state exit poll also put the turnout at 63.7 per cent, down on 2012. His campaign team said it was still an “incredible victory”.

“The percentage that we have just seen speaks for itself. It’s a mandate which Putin needs for future decisions, and he has a lot of them to make,” a spokesman told Russia’s Interfax.

Exit polls, published as soon as voting ended, showed that Putin’s closest opponent, Pavel Grudinin, was only projected to win 11.2 per cent.

During polling day, independent election monitoring group Golos reported hundreds of irregularities, including voting papers found in some ballot boxes before polls opened while webcams at polling stations were obstructed by balloons and other obstacles, but Russia’s electoral commission dismissed problems as minor.

Russian chess grand master and opposition politician Garry Kasparov tweeted: “Every free world leader who congratulates Putin on his ‘election’ is complicit in his global war on democracy. They undermine their own status as freely elected leaders.”