The Prime Minister glowered at Moscow’s foreign minister Sergey Lavrov, who the Russian president sent in his place to the G20 summit in Indonesia.
He told the meeting that Russia’s illegal war has “profound implications for us all” and “one man has the power to change all of this”.
“It is notable that Putin didn’t feel able to join us here. Maybe if he had, we could get on with sorting things out,” he said.
“Because the single biggest difference that anyone could make is for Russia to get out of Ukraine and end this barbaric war.
“That would be transformative for Ukraine, but for the world.”
Mr Sunak, the first British Prime Minister to come face to face with a Kremlin representative since the invasion, told the G20 “countries should not invade their neighbours”.
The PM insisted the UK will back Ukraine for “as long as it takes” and said the economic challenges the world is facing in the wake of covid have been made “much, much worse” by Russia’s invasion of Ukraine.
“The weaponisation of energy and food is totally unacceptable,” he said.
“Two thirds of Ukraine’s grain goes to developing countries, yet Russia has destroyed grain stores and blocked shipments.
“It is harming the most vulnerable people around the world. And this has nothing to do with sanctions.”
Ukraine’s president Volodymyr Zelensky addressed the summit remotely via video link, telling them he expects the fight against Russia to “go on for a little longer”.
The Prime Minister’s spokesman said Lavrov was “left in no doubt of the strength of feeling” about illegal invasion.
Lavrov addressed the group with the “misinformation and lies we’ve seen from Russia before”, he added.