A force spokesperson 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 three others were all arrested in March.
A man in his 50s was arrested on March 7, on suspicion of an offence contrary to Section 19 of the Public Order Act – publishing or distributing material likely to stir up racial hatred.
The Met said a second man in his 50s was arrested in Tunbridge Wells on March 14 on the same charge.
A woman in her 70s was arrested on March 21, also on suspicion of publishing or distributing material likely to stir up racial hatred.
All were interviewed under caution and released pending further investigation.
A Labour spokesperon said: "We welcome the police investigating these individuals’ alleged crimes.
“Antisemitism has no place in our society and we are committed to challenging and campaigning against it in all its forms."
