Netanyahu, the son of a historian, said the mufti played “a central role in fomenting the Final Solution”, as the Nazis termed their plan to exterminate the Jews.

The remarks were made in a speech to the World Zionist Congress about “the 10 big lies” told by Palestinians and their backers.

As supporters of the Israeli leader wondered what exactly he was doing, his critics said his claims were outrageous enough to give cover to Holocaust deniers.

The controversy erupted on the eve of Netanyahu’s state visit to Germany, where Holocaust denial is a crime. The Germans pushed back, telling the Israeli leader – very politely – that the Holocaust was their responsibility alone.

The speech was pure Netanyahu, delivered in his trademark blunt and conversational style. But what motivated his remarks on the mufti was not clear, though Palestinians deemed it classic incitement and historians of the Holocaust said he was wrong.

The mufti of Jerusalem “was a virulent anti-Semite, but we must always be careful in talking about the Holocaust”, Jonathan Greenblatt, national director of the Anti-Defamation League, warned on Twitter.

He added: “Even if unintended, the prime minister, by his words, plays into those who would trivialise or understate Adolf Hitler’s role in orchestrating the Final Solution”, which killed about six million Jews.Even Israeli Defence Minister Moshe Yaalon, a Netanyahu ally, said Hitler “initiated the Holocaust; the mufti joined him”.

Netanyahu, elected to a historic fourth term this year, has often claimed the mantle of leader of the Jewish people.

His remarks were intended to underline his contention that the root cause of Palestinian violence is not Israel’s 48-year-old military occupation of the West Bank, the building of Jewish settlements on lands that the Palestinians hope to make part of their future state or the partial trade and travel blockade of the Gaza Strip, but old and intractable hatred of Jews.

In speeches in 2013 and earlier this year, Netanyahu pointed to the mufti of Jerusalem as exemplifying deep Arab anti-Semitism. This time, the Israeli leader went further, claiming that the Palestinian religious leader gave Hitler the idea for the Final Solution.

Reaction in Israel – and across the Jewish world – came hard and fast. First, politicians were stunned. Then historians piled on. Then Netanyahu became fodder for social media memes and parodies.

Israeli opposition leader Isaac Herzog called Netanyahu’s charges “a dangerous historical distortion” that “minimises the Holocaust, Nazism and Hitler’s part in our people’s terrible disaster”.

Herzog noted that the Holocaust had already begun by the time the grand mufti met Hitler in November 1941.

“This wasn’t a speech by Jorg Haider,” Zehava Galon of the left-wing Meretz party wrote on her Facebook page, referring to the late leader of the far-right Freedom Party in Austria. “This wasn’t a snippet of Palestinian Authority President Mahmoud Abbas’ doctoral thesis”, which questions whether six million Jews were killed in the Holocaust. “This was an actual quote by the prime minister of the State of Israel, Benjamin Netanyahu, before the World Zionist Congress. It has to be seen to be believed.”

“Perhaps we should exhume the corpses of the 33,771 Jews murdered in Babi Yar in September 1941, two months before the Mufti and Hitler met, and bring them up to speed on the fact that the Nazis had no intention of destroying them,” Galon wrote.

Babi Yar was a site outside Ukraine’s capital where German troops carried out a mass killing of Jews and local collaborators.

Saeb Erekat, a Palestinian leader and former peace negotiator, said, “Netanyahu hates Palestinians so much that he is willing to absolve Hitler of the murder of six million Jews.”

Husseini was a religious and political leader of the Arab population in Palestine during the British Mandatory period between the two world wars. He fomented deadly riots over the Zionists coming to Palestine, opposed mass migration of Jews and allied with Hitler and the Nazis during the second world war, in part because of his opposition to British rule. The mufti spent the war in Berlin, broadcasting Arabic-language propaganda and incitement against Jews and the Allies.

As he boarded his plane to Germany on Wednesday, Netanyahu attempted some damage control, saying he had been misunderstood.

“It is absurd. I had no intention to absolve Hitler of responsibility for his diabolical destruction of European Jewry,” he said. “Hitler was responsible for the Final Solution extermination of six million Jews. He made the decision.”

However, Netanyahu held firm to his characterisation of Husseini: “The mufti was instrumental in the decision to exterminate the Jews. We must not ignore the importance of his role. The mufti repeatedly suggested that the Jews should be exterminated. He considered it an appropriate solution to the Palestinian question.”

Steffen Seibert, a spokesman for German Chancellor Angela Merkel, said: “All Germans know the history of the murderous race mania of the Nazis that led to the break with civilization that was the Holocaust,” Reuters news agency reported.

“This is taught in German schools for good reason; it must never be forgotten,” Seibert said. “And I see no reason to change our view of history in any way. We know that responsibility for this crime against humanity is German and very much our own.”