Jacob Rees-Mogg has said Brexit allowed Britain to show "global leadership" over Ukraine, making it "impossible for Putin to succeed".
The 53-year-old former Tory cabinet minister made the argument after being asked on Sky News' Sophy Ridge On Sunday programme about what had been the main benefits of leaving the EU.
Mr Rees-Mogg said: "The leadership shown by Boris Johnson, which he could only do because he was not bound by sincere cooperation, ensured that a coalition was set up which made it impossible for [Russian President Vladimir] Putin so succeed.
"We were able to show global leadership over Ukraine. 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."
He echoed comments made by the former prime minister, Mr Johnson, in Washington DC in February.
Mr Johnson said quitting the European bloc allowed Britain to "do things differently" while providing weapons to Kyiv.
"I seriously think that it was in part because of Brexit that we were able to take a decision and to have an approach that was very distinct from the old EU approach, which was, by the way, all governed by the fabled Normandy Format, which was agreed in Normandy in 2014," he said.
"For reasons that are now obscure to me, the British government decided they did not want to be involved in this. France and Germany led it, that was the EU framework.
"If we'd stuck with that, I don't believe we would have delivered the NLaws [anti-tank weapons] and I think we would have taken a very different approach, to be perfectly frank.
"I think because of Brexit we've been able to do things differently and I hope in a way that has been useful to Ukraine," Mr Johnson added.
Since the Russian invasion, the UK has committed £4.6bn in military assistance to Ukraine, second only to the US, and is also training thousands of soldiers from the country.
This week, the government announced that it would be sending long-range Storm Shadow missiles to Ukraine.
The EU is also providing non-lethal and lethal arms, the first time the bloc has ever supplied such weapons to a third country.
It has committed just over €4.6bn (£4.04bn), and many European countries have donated military hardware such as Leopard tanks.