He has since repeated the claim, and later told the BBC that he stood by his comments and insisted Churchill was “indisputably a white supremacist and a mass murderer".
Greer also added that the trouble with the UK was that “we are almost only allowed to talk about Churchill through the prism of not just the Second World War, but the war in Europe".
His comments were criticised widely by Conservatives and Churchill fans. Tory deputy chairman James Cleverly called it the "most superficial and inaccurate assessment".
Piers Morgan took to Twitter, where he responded to Greer’s comments with the following: "And you’re a thick ginger turd who’d be spewing this filth in German if it wasn’t for Churchill."
He later invited Greer on Good Morning Britain to debate the issue, saying he was “gutless as well as a thick ginger turd” if he didn’t accept.
Piers Morgan is a fierce supporter of the late PM, and last year in a GMB segment with Afua Hirsch and Gisela Stuart about Churchill, he called him "the man that saved the world from Adolf Hitler".
Author Hirsch had responded at the time:
This is the problem. Why can’t we accommodate a reality where someone on the one hand won the war and beat fascism, but on the other hand had racist white supremacist views that also led to the deaths of millions of people?
Churchill played a vital role as a bulwark against Nazism, but his legacy isn’t as clean as some might suggest. It has been well documented that he has said some racist statements.
Some 35 years later, he told the Palestine Royal Commission: "I do not admit... a great wrong has been done to the Red Indians of America or the black people of Australia.
I do not admit that a wrong has been done to these people by the fact that a stronger race, a higher-grade race... has come in and taken their place.
He defended British use of concentration camps in South Africa, claiming it produced “the minimum of suffering”, despite estimations stating the death toll in such camps amounted to 42,000 Boers and black South Africans.
According to John Charmley, author of Churchill: The End of Glory, the late MP believed in racial hierarches and eugenics.
In 1919 he wrote in a memo during his role as minister for war and air:
I cannot understand this squeamishness about the use of gas.
This was in reference to chemical weapons, mostly against Kurds and Afghans.
Churchill is also known to have supported clearances in Kenya's highlands of the local Kikuyu people, who he called "brutish children".
During the suppression of the Mau Mau Uprising, under his post-war premiership, 11,000 Kenyans died and around 100,000 were forced into detention camps where brutal torture took place, with Barack Obama's grandfather believed to have been among them.
But defenders of the wartime prime minister, such as Piers Morgan, insist his comments but be taken int he context of the time they were spoken, and that his success in fighting Nazi Germany should be his overriding legacy.