Brexit helped to prevent Russian tyrant Vladimir Putin from successfully invading Ukraine, Jacob Rees-Mogg has claimed.
The hard-line Tory Eurosceptic suggested a "mucky compromise" would have been made with the Kremlin if the UK had still been tied to Brussels.
Mr Rees-Mogg, a former Cabinet Minister, argued that Boris Johnson would not have been able to offer the same level of British support to Kyiv if the UK had remained in the bloc.
He told Sky News's Sophy Ridge On Sunday programme: "Putin would probably have invaded Ukraine successfully if the UK had been bound in by the requirement of sincere cooperation and had had to follow a Franco-German line in dealing with Russia, which is what we did in 2014."
Pressed on whether he genuinely believed this, the former Cabinet Minister said: "I think the leadership shown by Boris Johnson, which he could only do because he was not bound by sincere co-operation, ensured that a coalition was set up that made it impossible for Putin to succeed.
“And if I think that hadn’t been the case, we’d have been bound by this concept of sincere cooperation, we’d have had the mucky compromise that was delivered in 2014 when Russia invaded the Crimea."
Mr Johnson previously said quitting the EU allowed the UK to "do things differently", such as the delivery of anti-tank weapons systems, known as NLAWs, to Ukraine.
Mr Rees-Mogg said he believed it was a mistake to get rid of Mr Johnson, but deposing Rishi Sunak would be an "even bigger mistake".
"The Tory Party would be toast if we change leader again... but that doesn't mean we agree with him on every policy," he said.
But Energy Secretary Grant Shapps claimed the party was "buzzing with ideas" despite a fresh outburst of Tory infighting following the party's disastrous local election results.
Mr Sunak has been in the firing line following the loss of more than 1,000 councillors and his decision to scale back his promise of a post-Brexit bonfire of EU laws.
Disgruntled right-wingers gathered at a Conservative Democratic Organisation (CDO) conference on Saturday, where former Home Secretary Priti Patel accused the Prime Minister of overseeing "managed decline" of the party.
The CDO, led by donor Lord Peter Cruddas and former MEP David Campbell Bannerman, was behind the "Get Boris on the Ballot" campaign after the ex-PM was ousted last year.
