Jeremy Corbyn has said he is "sincerely sorry" for pain caused by anti-Semitism which occurred in "pockets" within the Labour Party.
In a statement on Sunday, the Labour leader said he "utterly" condemns anti-Semitism and that as leader he "will not tolerate any form of anti-Semitism that exists in and around our movement".
He said: "We recognise that anti-Semitism has occurred in pockets within the Labour Party, causing pain and hurt to our Jewish community in the Labour Party and the rest of the country.
"I am sincerely sorry for the pain which has been caused."
Earlier on Sunday, senior Labour figures defended Mr Corbyn amid the row over his apparent support for an anti-Semitic mural.
Shadow transport secretary Andy McDonald told Sky News' Sunday with Niall Paterson that the Labour leader "hasn't got an anti-Semitic bone in his body", while deputy leader Tom Watson said Mr Corbyn had expressed "deep regret".
The mural, made by street artist Mear One, depicted a group of Jewish financiers and white businessmen playing a Monopoly-style game on a board balanced on the backs of people.
Included in the portrait, which was removed by Tower Hamlets Council after a number of complaints were made, was an activist holding a banner which read: "The new world order is the enemy of humanity."
Mr Corbyn left a comment on a Facebook post by Mear One, real name Kalen Ockerman, in 2012 after the artist revealed his work was set to be whitewashed.
The Labour MP wrote: "Why? You are in good company. Rockerfeller (sic) destroyed Diego Viera's mural because it includes a picture of Lenin."
Mr Corbyn was criticised for initially expressing "sincere regret that I did not look more closely at the image I was commenting on, the contents of which are deeply disturbing and anti-Semitic" rather than issuing an apology.
Before his apology on Sunday evening, his statement read: "In 2012 I made a general comment about the removal of public art on grounds of freedom of speech. My comment referred to the destruction of the mural Man at the Crossroads by Diego Rivera on the Rockefeller Center.
"That is in no way comparable with the mural in the original post. I sincerely regret that I did not look more closely at the image I was commenting on, the contents of which are deeply disturbing and anti-Semitic.
"I wholeheartedly support its removal.
"I am opposed to the production of anti-Semitic material of any kind, and the defence of free speech cannot be used as a justification for the promotion of anti-Semitism in any form. That is a view I've always held."
As a result of the concern regarding Mr Corbyn's apparent support of anti-Semitism, the Jewish Leadership Council (JLC) has called on members of the Jewish community to gather in Parliament Square on Monday ahead of a Parliamentary Labour Party meeting.
The JLC accused Jeremy Corbyn of a "systematic failure to understand and deal with antisemitism" and said that Jewish community leaders would hand deliver a letter to the PLP meeting.
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Mr Corbyn has said that Labour must demonstrate a "total commitment to excising pockets of anti-Semitism that exist in and around our party" despite having launched an inquiry in 2016 into allegations of anti-Semitism in the party.
That followed high-profile comments by Labour Party members which were considered to be anti-Semitic and found that anti-Semitism was not more prevalent within the party that it was any other party.