Boris Johnson accused Tucker Carlson of infecting people's minds with "bad ideas" about Putin.
The former UK prime minister said Republicans seem to be "intimidated" by Carlson's perspective.
The Fox News host has echoed Kremlin talking points, whereas Johnson has been a fierce defender of Ukraine.
Former UK Prime Minister Boris Johnson accused Fox News host Tucker Carlson of infecting people's minds with "bad ideas" about what Russian President Vladimir Putin stands for.
Speaking on Wednesday during a panel discussion with the Atlantic Council, Johnson said: "I've been amazed and horrified by how many people are frightened of a guy called Tucker Carlson.
"Has anybody heard of Tucker Carlson? What is it with this guy? All these wonderful Republicans seem somehow intimidated by his perspective."
Johnson, who is on a high-profile speaking tour of the US, told the think tank's audience that he hasn't watched anything that Tucker Carlson has said, but that he's "struck by" how often his name comes up in conversations.
"Bad ideas are getting into, starting to infect the thinking around the world about what Putin stands for, what he believes in, it's a disaster," Johnson said.
"He stands for war, aggression, systematic murder, rape, and destruction. That's what he stands for."
Both before and after Russia's invasion of Ukraine, Carlson has been accused of parroting Kremlin talking points.
In fact, according to Mother Jones' reporting on a leaked war memo, back in March 2022, the Kremlin instructed Russian state media to feature Carlson "as much as possible" because of his criticism of the US and NATO's role in Ukraine.
Shortly before the invasion, with tensions already high, Carlson said on Fox News: "Democrats want you to hate Putin, anything less is treason."
And after the war broke out he continued to echo pro-Putin talking points. In May 2022, Carlson baselessly claimed that the US government's involvement in Ukraine was aimed at deposing Putin as "payback for the 2016 election."
In July 2022 he suggested that Italy posed a bigger threat to the world than Russia because of its slightly larger economy. "The Italians, in other words, are in a better position to take over the world than Vladimir Putin," he said.
Johnson, on the other hand, has been a fierce defender of Ukraine and Ukrainian President Volodymyr Zelenskyy.
Last month, despite resigning as UK prime minister in July 2022 following scandals and a cabinet revolt, Johnson visited Kyiv, where Zelenskyy greeted him as a "true friend of Ukraine."
Fox News did not immediately respond to Insider's request for comment, but Carlson told the viewers of his show on Wednesday evening that Johnson's remarks "shocked" him.
He described the former prime minister as a "coward" and a "liar," adding that Fox News had invited Johnson to appear on his show just "hours before" the Atlantic Council comments, per Mediaite.