Foreign Secretary Ed Miliband has directly told Russia's foreign minister Sergei Lavrov that "we all know you are the aggressor" in the Ukraine conflict, while highlighting the killing of innocent civilians.
Speaking at the G20 summit in Atlanta, Georgia, Mr Miliband also said Moscow was "not winning this war" because of the "courage of the Ukrainian people" and the solidarity of its allies.
Direct Address to Moscow
In his intervention at Friday's meeting, Mr Miliband said: "Let me say this directly to the Russian foreign minister – we all know who the aggressor in this war is.
"Let's talk about what happened at Dnipro railway yesterday. Only yesterday your drones attacked and killed 15 people.
"And there are countless examples like this of you killing innocent civilians throughout this war.
"We all know you are the aggressor. We all know you started this war four and a half years ago with the full-scale invasion of Ukraine.
"And Putin thought then he would win this war easily. But you are not winning this war.
"Thanks to the courage of the Ukrainian people and the solidarity of countries round this table, you are not winning.
"If you had the courage to tell the truth and to do what is right you would tell Putin that he is not winning this war and will not win."
Pressure on Putin
In what will be seen as a veiled sideswipe at US President Donald Trump, who recently waived sanctions against the Kremlin, Mr Miliband stressed the need for all countries to apply pressure and deprive Russian leader Vladimir Putin "of the revenues that perpetuate this barbaric war".
Mr Miliband made his comments at a meeting of foreign ministers from the world's leading economies. Some countries had expressed concern that the US had invited Russia amid devastating attacks on its neighbour.
Earlier a planned photocall at the start of the summit was scrapped after Mr Miliband and other European counterparts refused to be pictured with Mr Lavrov – a close, long-standing ally of Mr Putin.
Call for Lasting Peace
Mr Miliband also told the meeting: "If we are serious about our values and our interests we must also work harder to secure just and lasting peace in Ukraine.
"Russia's war continues to cause colossal global harm, including the deaths of thousands of innocent civilians and disruption that hits energy and supplies and worsens food insecurity.
"An assault not only on Ukraine but on us all, trampling international law, sovereignty and self determination – core principles on which we all depend.
"This war is not simply a test for Europe or for Nato – it requires all of us to apply economic and diplomatic pressure to deprive Putin of the revenues that perpetuate this barbaric war."