Speaking in Davos, Johnson said Putin wanted to present the war in Ukraine as a "nuclear standoff between NATO and Russia."

"Nonsense. He's not going to use nuclear weapons. He's like the fat boy in Dickens. He wants to make our flesh creep," Johnson continued.

"He wants us to think about it. He's never going to do it," he added.

"Fat boy" is a character in Dickens' first novel, The Pickwick Papers, who appears to delight in scaring a trembling old woman by telling her "I wants to make your flesh creep."

Johnson argued that Putin would never use nuclear weapons because "we put him into a complete economic cryogenic paralysis" and that using them would lead China and India to turn against Moscow.

Johnson, who resigned in July after a series of scandals, was one of Ukraine's closest allies while in office.

He made the comments about Putin while arguing that Western nations should stop focusing on the Kremlin leader and provide more weaponry to Ukraine to enable the country to defend itself.

"They're going to win. We need to help them to win as fast as possible," Johnson said.