The American broadcaster has been the “stooge of the tyrant, the dictaphone to the dictator and a traitor to journalism”, he said.
He accused the former Fox News host of betraying “viewers and listeners around the world” for not taking the Russian leader to task for “the torture, the rapes, the blowing up of kindergartens” in Ukraine, “not once did he even try to dam the flow of lies” in a column for Mail+.
Putin’s message to America was straight out of the Hitler playbook, he said “Stay out of this conflict... — and soon we can all be at peace.”
The only difference was that Hitler delivered his message, in June 1940 shortly after he invaded France, through the newspapers of WR Hearst and a German-American journalist called Von Wiegand, he suggested.
Earlier Rishi Sunak labelled “clearly ridiculous” Putin’s claim the West and Nato are to blame to the war in Ukraine.
Mr Johnson also attacked on the allegation the UK government persuaded the Ukrainians to fight on, rather than surrender in the wake of the invasion in the spring of 2022.
“Nothing and no one could have stopped those lion-hearted Ukrainians from fighting for their country — and nothing will,” he said.
He said he hoped and believed that if President Trump is elected again he would “confound his critics… (and) give arms to the Ukrainians”.
And he urged Republicans politicians currently blocking aid to Ukraine, “for God’s sake remember who you are. You are the heirs of Ronald Reagan, the leaders of the last best hope of earth.”
The two-hour, seven-minute interview started with a long diatribe from Putin on Russian history and its relationship with Ukraine.
The White House has warned against believing “anything” Putin said in the interview.
Former prime minister Mr Johnson was one of the first Western leaders to visit Kyiv after Russian invasion of Ukraine. However, he also came under fire for plans to visit the war-torn country after his exit from office. The Independent revealed that senior military figures thought he was “looking for publicity” in a warzone and urged him not to go.