Jeremy Corbyn hosted a protest event in Parliament, promoted as “Auschwitz to Gaza” comparing the Jewish state to Nazis, on Holocaust Memorial Day when Britons remember those killed by Nazis and in other genocides.

The Labour leader spoke at and opened a talk in the House of Commons, entitled “Never Again for Anyone – Auschwitz to Gaza”, in 2010 when he was a backbench MP.

The main talk was called “The Misuse of the Holocaust for Political Purposes”. Mr Corbyn has now issued an unusual apology since it was exposed by The Times.

He acknowledged he had appeared with people “whose views I completely reject” and apologised for the “concerns and anxiety” it caused.

Mr Corbyn said: “The main speaker at this Holocaust Memorial Day meeting was a Jewish Auschwitz survivor. Views were expressed at the meeting, which I do not accept or condone.

“In the past, in pursuit of justice for the Palestinian people and peace in Israel/Palestine, I have on occasion appeared on platforms with people whose views I completely reject. I apologise for the concerns and anxiety that this has caused.”

The Labour MP John Mann said it was “extraordinary” for an MP to have hosted such an event and questioned why people would “protest” on a day for remembering victims of genocide.

“It breaches any form of normal decency. I am not sure how he got himself into that situation but I am pleased he apologised,” he said on BBC Radio 4’s Today programme.

Also Wednesday, the Campaign Against Antisemitism (CAA) referred Labour to the Equality and Human Rights Commission and made a complaint to Labour about Mr Corbyn’s handling of anti-Semitism.

The CAA wrote in a letter to the watchdog: “We charge that the party has, through years of deliberate or reckless dereliction of its duty to enforce its own rules, created an atmosphere in which Jewish members and/or associates are discriminated against.”

The day before, on Tuesday, a recording of a Labour National Executive Committee (NEC) member and key ally of Mr Corbyn berating Jewish “Trump fanatics” for inventing claims of anti-Semitism in the party was published.

Mr Corbyn is yet to comment on or condemn the remarks, and was present at the meeting when they were made.

Also at that meeting, the NEC discussed the fact Labour has failed to adopt an internationally recognised definition of anti-Semitism, which has exacerbated the long-running scandal.

The new code was rejected as “toothless” by angry campaigners and community groups when it was first released last month.

Labour politicians including Dame Margaret Hodge, who have attacked Mr Corbyn for alleged anti-Semitism, are currently being investigated by the party, as well as over 250 complaints of anti-Semitic abuse amongst the membership.