Defense secretary Ben Wallace was overheard giving a less-than-tactful assessment of President Putin, as Shehab Khan reports
Mr Wallace, heard chatting with serving military personnel at the Horse Guards building in Westminster, said the Russian president had gone "full Tonto" with his escalation of tensions with Ukraine.
He said Mr Putin has made the mistake of having no allies in his actions, comparing him to Tsar Nicholas I during the Crimean War.
The Cabinet minister said there are 1,000 British military personnel on stand-by to respond to the Ukraine crisis, adding: "The Scots Guards kicked the backside of Tsar Nicholas I in 1853 in Crimea - we can always do it again." He continued: "Tsar Nicholas I made the same mistake Putin did... he had no friends, no alliances."
His comments were mocked online by social media users who pointed out Russia did not possess nuclear weapons back in the 1800s.
One Twitter user wrote: "Unlike Putin now, Nicholas didn’t have nuclear weapons back then.When you have to bring up the past, you have nothing, like Johnson bringing up Churchill."
His comments came amid warnings from Foreign Secretary Liz Truss that Russia is planning a "full-scale" invasion of its south-western neighbour that "won't just stop at Ukraine".
She told ITV News Mr Putin could be planning to takeover "vast swathes of eastern Europe", saying the strong-arm leader has "also talked about turning the clock back to the 1990s" when Russia had control of former Soviet Union countries including Nato members Estonia, Latvia and Lithuania.
Boris Johnson announced at PMQs that the UK would be sending further military aid to Ukraine "in light of the increasingly threatening behaviour" from Russia.
"This will include lethal aid in the form of defensive weapons and non-lethal aid," he added.
Britain has previously made clear it would not engage in any military combat against Russia in Ukraine and soldiers are only stationed in the area to provide humanitarian support should an invasion make that necessary.
Downing Street would not give further details on the military equipment being provided to Ukraine for "security reasons" although it is understood no British personnel will be sent.
Mr Wallace said: "It's going to be a busy Army. Unfortunately we've got a busy adversary now in Putin, who has gone full Tonto." Tonto is a fictional Native American character from the American Wild West, who, along with the Lone Ranger, fought outlaws.
The defence secretary's comments, made while sat next to Home Secretary Priti Patel, came in a room dominated by a large painting depicting the Battle of Inkerman, a major engagement during the Crimean War. Mr Wallace's assessment of Mr Putin's mental state came after Prime Minister Johnson accused the Russian leader of being "in an illogical and irrational frame of mind". Mr Wallace told reporters he was keeping the possibility of sending further weapons to Ukraine "under constant review", adding: "We're in a pretty good position to deliver any type of aid pretty quickly to Ukraine, no matter what that aid is."
He suggested that Russian forces invading Ukraine could be followed by a mobile crematorium to help disguise the number of casualties inflicted during the potential war. "Fundamentally, when you have over 60% of your combat forces poised on the borders of another state, the overwhelming scale of the Russian intimidation and forces - including some pretty horrendous weapons systems - are pretty worrying. "And we also expect to see some of the things they've done previously. Previously, they've deployed mobile crematoriums to follow troops around the battlefield, which in anyone's book is chilling. "If I was a soldier, and knew that my generals had so little faith in me that they followed me around the battlefield in a mobile crematorium, or I was the mother or a father of a son, potentially deployed into a combat zone, and my government thought that the way to cover up loss was a mobile crematorium - I'd be deeply, deeply worried."