"There is only one thing that gives the Kremlin succour and lends false credibility to its propaganda onslaught, and that is when politicians from the targeted countries join in the effort — whether wittingly or not — to create doubt where there is none and sow confusion where there is clarity. Sadly, I am driven to the conclusion that Jeremy Corbyn has joined this effort," Johnson said in the article published by The Sunday Times.
The UK diplomat said that Corbyn refused to clearly put the blame for the incident on Moscow citing his "infantile leftist background," due to which the Labour Party politician sympathizes for "any country, any movement, however unappealing, that is hostile to Britain."
"This is cynical nonsense and Jeremy Corbyn shames himself by lending it succour. Truly he is the Kremlin’s useful idiot," the foreign secretary added.
Johnson said that the Russian side had attempted to "bury awkward facts beneath an avalanche of lies and disinformation" adding that Moscow had "invented 29 separate theories" about the Salisbury incident.
Soon after the poisoning incident, a number of UK officials, including Johnson and the UK prime minister, put the blame on Russia. The United Kingdom believes the Skripals were exposed to the A234 nerve agent, related to the Novichok-class nerve agents developed in the Soviet Union.
Following the statement, Corbyn said that Johnson should clarify his claims that the poisoning substance was produced by Russia.
On March 4, Skripal and his daughter Yulia were found unconscious in the UK city of Salisbury. London has accused Moscow of involvement in the incident, and soon after the incident, announced the expulsion of 23 Russian diplomats.
Over 25 countries have since expelled Russian diplomats "in solidarity" with London. Moscow has denied having any role in the poisoning, pointing to the lack of evidence provided by London to substantiate its accusations.