Russia's behaviour in Syria has been likened to the Nazis as MPs prepared to take part in an urgent debate on the "unfolding humanitarian catastrophe" in the country.
Tory former chief whip Andrew Mitchell accused Moscow of "shredding the international rules-based system of law" as condemnation grows over its alleged role in the bombing of a UN aid convoy.
MPs agreed to an urgent debate in the first public business in the House of Commons on Tuesday.
Defence Secretary Sir Michael Fallon is among those who have accused Russia of helping the Syrian government in bombing its own people, which it denies.
But former international development secretary Mr Mitchell went further, comparing Moscow's role to that of the Nazis during the Spanish Civil War.
He condemned Russia for its part in what he called the "unfolding humanitarian catastrophe in Aleppo, and more widely across Syria".
He told the Commons on Monday: "The use of incendiary weapons, munitions such as bunker buster bombs and cluster bombs - the UN make clear that the systematic use of such indiscriminate weapons in densely populated areas amounts to a war crime.
"We are witnessing events which match the behaviour of the Nazi regime in Guernica in Spain.
"Russia is shredding the international rules-based system of law.
"They are destroying the United Nations and its ability to act, in the same way the Germans and the Italians destroyed the League of Nations in the 1930s."