The senior ally of Jeremy Corbyn, who was exposed by the JC for claiming Jewish "Trump fanatics" are making false claims of antisemitism within Labour, has apologised and pledged to undertake "equalities training".
Pete Willsman, a member of Labour's national executive committee (NEC), issued a statement after his comments caused widespread anger and dismay after a recording of them was given to this paper.
He launched into his angry rant at the NEC's July 17 meeting, where it adopted a code of conduct on Jew-hate and rejected the internationally-recognised definition of antisemitism, triggering a huge row.
But in Mr Willsman's statement - which is believed to have been made after consultation with Mr Corbyn's office - he also claimed that antisemitism was not "widespread" within Labour.
On Tuesday evening, Mr Willsman said he was "sorry" and "deeply regretted" his behaviour, which led to calls for Mr Corbyn to expel from the party.
He added: "Having sat on the NEC for many years, I am of course aware of appalling instances of antisemitism within our party, and am wholly determined to rooting it out of our movement.
"I do not believe antisemitism is 'widespread' in the Labour Party, and that was what my comments were trying to refer to, but we do have a problem which needs stamping out.
"One antisemite is one too many.
"I recognise the offensive nature of my comments and that, in diminishing the experiences of those who face antisemitism in our party and society, I showed a lack of the sensitivity required for discussions around racism."
Mr Willsman added that he would be "referring" himself to "receive equalities training" so he could "better understand how to approach discussions of such issues in a respectful way".
A separate recording, obtained by Sky News, revealed Mr Willsman told the NEC that Mr Corbyn sought his advice over Shami Chakrabarti's report into allegations of antisemitism within Labour.
The recording, from 19 July 2016, was shortly after Labour MPs had overwhelmingly backed a no-confidence motion in Mr Corbyn.
In the recording, Mr Willsman describes Mr Corbyn as his "mate of 40 years".
He says: "The phone went and it was Jeremy. He was texting me. He said: 'I'm sitting on the Somme waiting to make a speech, I've got a few minutes, could you please text me the recommendations in Shami's report we need to be a bit careful about?'.
"By that point I'd read it and I texted him back...
"And I thought 'this is a chap who's cracking up, he's sending me texts from the Somme about Shami's report'. So I had a very good laugh."
The JC asked Mr Corbyn's office for comment on audio of Mr Willsman's July 17 speech - in which he also accused "70 rabbis" of making allegations of Jew-hate without evidence.
But a spokesman directed us to Mr Willsman's statement.