A London councillor is to be investigated by the Labour Party over a post he shared on Facebook which claimed Jews were warned about the 9/11 attacks.
Lambeth Council member Irfan Mohammad said he "reposted a video without recognising that it contained anti-Semitic content" in 2015.
He has apologised "unreservedly".
Lambeth Labour chief whip Jane Edbrooke said the allegation of anti-Semitism would be taken "extremely seriously".
The post shared on the social networking site stated: "Jews working in the World Trade Centre received a text message before the incident 'Do not come to work [on] September 11'".
It was brought to light by the Campaign Against Anti-Semitism which described the post as "utterly appalling".
'No place for anti-Semitism'
In a letter posted on Twitter, Mr Mohammed, who is also a member of the Lambeth Inferfaith Forum, asked Ms Edbrooke to begin disciplinary action.
The letter read: "I reposted a video without recognising that it contained anti-Semitic content.
"This was a stupid thing and thoughtless thing to do and I recognise that it was an anti-Semitic act.
"It is totally unacceptable and it was my mistake which I do not shy away from.
"I apologise unreservedly, I completely accept that I have hurt the Jewish community through my action."
Ms Edbrooke said: "We take any allegation of anti-Semitism extremely seriously and condemn anti-Semitism in all its forms. There is no place in our party for anti-Semitism.
"Councillor Irfan Mohammed has apologised and there will be an investigation."
Mr Mohammed, who was not a councillor when he shared the post, was elected in 2018.
He said he would be writing to synagogues in Lambeth to personally apologise, and was "keen to listen and learn from them."