A criminal investigation has been launched into allegations of anti-Semitic hate crimes within the Labour Party.
The Metropolitan Police are acting on a dossier of information handed to Commissioner Cressida Dick.
A spokesman said: "On Tuesday September 4, the Met Commissioner was handed a folder of paperwork following a radio interview with LBC Radio in Leicester Square.
"The complainant alleged that the documentation included evidence of anti-Semitic hate crimes.
"The contents have been examined by specialist officers.
"A criminal investigation has commenced into some of the allegations within the documentation.
"Early investigative advice is being sought from the Crown Prosecution Service."
LBC received an internal Labour dossier detailing 45 cases involving messages posted by party members on social media, including one which read: "We shall rid the Jews who are a cancer on us all."
The broadcaster passed the leaked material to former senior police officer Mak Chishty, who said that 17 instances should have been reported to the police for investigation, and another four were potential race hate crimes.
These were the message detailed above; the sharing of a link to an allegedly anti-Semitic blog, and an entry referring to "a Zionist Extremist MP ... who hates civilised people, about to get a good kicking".
The fourth related to a party member being accused of putting a child through "10 years of hell", using racial slurs against him and referring to him as "Jew boy".
It was also alleged that the member had chased a girl, aged six or seven, around with air freshener, saying she smelled of curry and calling her "a chocolate monkey".