Pro-Ukraine counter-protesters led by campaigner Peter Tatchell confronted activists calling for the UK to stop sending arms to Ukraine in central London.
Mr Tatchell shouted “Chamberlain” – a reference to prime minister Neville Chamberlain’s policy of appeasing Adolf Hitler’s Nazi regime – in reply to protesters who angrily accused him of being an “American stooge”.
He was one of a group of 30 who interrupted a rally by the Campaign for Nuclear Disarmament (CND) and Stop the War coalition outside the BBC’s Broadcasting House.
His fellow protesters chanted “arm, arm, arm Ukraine, put an end to (Russian President Vladimir) Putin’s reign” and “self-defence is no offence”.
Mr Tatchell told the PA news agency: “We’re here to protest Stop the War over its opposition to Ukraine. Their stance would leave Ukraine defenceless and result in Russia occupying and annexing all of Ukraine.
“Russia is a fascist, imperialist state, and all progressive people should oppose the Putin regime and Russia’s war of aggression.
“We should arm Ukraine in the same way that we armed anti-Nazi resistance during the Second World War. This is a war between Ukrainian democracy and Russian fascism.”
His group held a banner reading “Victory to Ukraine, arm Ukraine to defeat Russian imperialism”.
CND and Stop the War claim Russia’s invasion was partially caused by “Nato expansion” in eastern Europe.
Their protesters held placards saying “Peace now!”, “No to War” and “Wages not Weapons”, with one man flying an inflatable anvil that read: “Is this anvil really cast iron? Are the Biden gang’s alibis?”
Stop the War organiser Terina Hine, 54, said Ukraine would become the “Afghanistan of Europe” if it and its supporters did not stop “backing Putin into a corner”.
She told PA: “If we carry on backing Putin into a corner, there’s a very high chance that it will escalate on a nuclear level.
“It’s likely the war will be very long and very drawn out and if it carries on the way that it has been doing so far, it will lead to thousands upon thousands of deaths and Ukraine becoming the Afghanistan of Europe.
“The war will eventually end by peace negotiations. So why not do that now?
“Anybody who has even dared mentioned anything along those lines has been accused of being a traitor, or an appeaser or any of those other terms that are used as an attack line against people who just want peace.”
Tom Unterrainer, 42, chairman of the CND, said negotiations were inevitable and claimed there is no reason to delay them.
He told PA: “Everybody knows that this will end with negotiations. Everybody knows that this will end with diplomacy.
“So the only question on the table now is how much destruction will there be in Ukraine, how many Ukrainians will die and how much closer will we get to the nightmare of nuclear use.
“Given that there’s a wide recognition that this conflict will end in negotiation, given that there’s such a sharply posed nuclear threat, then now is the time to negotiate. We do not have the time to wait.”
The Met Police has been approached for comment.
