Ben Wallace made the unguarded comments while chatting to serving military personnel at the Horse Guards building in Westminster on Wednesday.
Speaking about the situation in Ukraine, he said: “It’s going to be a busy Army.
“Unfortunately we’ve got a busy adversary now in Putin, who has gone full tonto.”
Maria Zakharova, Russia’s Foreign Affairs Ministry spokeswoman, was asked about the comments by Sky News at a press briefing on Friday.
According to the translation on Sky News, she said it was “surprising that such evaluations are given by (the) defence minister of the UK regarding authorities of a different state”.
She added: “I think he could have thought up of similar adjectives… thinking of (the) British Prime Minister if we talk about personal judgment.”
Earlier on Friday Mr Wallace, a former Scots Guards officer, was asked on Sky News whether he was now even more convinced Mr Putin had “gone full tonto” and was acting irrationally.
“I certainly think what he is doing is deeply irrational,” he said.
“I certainly think he has gone full tonto.”
He said: “No one else in their right mind would…