A fourth man has been arrested in connection with a dossier of alleged anti-Semitic offences by members of the Labour Party.
The 44-year-old man was arrested in Newham on Wednesday and is in police custody.
An investigation was launched into alleged anti-Semitism among party members in November after a dossier of evidence was handed to Metropolitan Police Commissioner Cressida Dick.
A Met Police spokesman said: “We can confirm police have arrested a fourth man, aged 44, on Wednesday, 1 May, on suspicion of an offence contrary to Section 19 Public Order Act 1986 – publishing or distributing material likely to stir up racial hatred.
“A warrant was executed at an address in Newham. The man is currently in police custody.”
The man is understood to be a Labour member and the party press office has yet to issue any further information.
Three others were arrested in March on suspicion of publishing or distributing material likely to stir up racial hatred.
They were a man in his 50s, arrested in Birmingham on March 7, a second man in his 50s held in Tunbridge Wells on March 14 and a woman in her 70s in Wandsworth, south London, on March 21. All three have been released pending further inquiries.
The investigation was prompted by an internal Labour dossier detailing anti-Semitic messages on social media allegedly posted by Labour Party members, which was obtained by LBC radio.
Reports at the time suggested the documents included details of 45 cases, including one which allegedly read: “We shall rid the Jews who are a cancer on us all.”
Campaign Against Antisemitism chairman Gideon Falter said the police must continue investigating and suggested there were more dossiers that should be handed over.
He said: “I am pleased that four arrests have now been made after I reported the secret Labour Party dossier to the Commissioner live on air, but the dossier contains many more hate crimes which must also result in arrests.
“Moreover, officers must demand that the Labour Party hands over further dossiers we know of and seize them if it refuses, so that police can investigate whether the Labour Party’s decision to keep evidence of crimes and admissions of guilt secret actually results in criminal liability for those responsible within the Party.”
It is understood that disciplinary action was taken by Labour against the three individuals believed to be under investigation, and they are no longer party members.
A party spokesman said Labour was committed to challenging anti-Semitism.
He said: “We welcome the police investigating these individuals’ alleged crimes.
“Anti-Semitism has no place in our society and we are committed to challenging and campaigning against it in all its forms.”