Benjamin Netanyahu's son Yair has sparked anger by wishing "good luck" to Hungarian Prime Minister Victor Orbán in tomorrow's European elections, calling them "true friends of Israel and the Jewish people".
Yair Netanyahu also wished the same to Brexit Party leader Nigel Farage and Italian Interior Minister Matteo Salvini, who leads the League Party.
The tweet triggered a backlash in which Mr Orban was labelled a "notoroius antisemite" and the prime minister's son was accused of "cheering on fascists".
The 27-year-old, who is prone to outbursts on social media, later tweeted people who "went bananas" about his his message were "crazy" and said Jeremy Corbyn and other leftwing figures were themselves "actually antisemites and racist!"
He then tweeted a photo of himself with Mr Orbán, saying: "Take that!"
Mr Orbán has been accused of fuelling antisemitism with his aggressive campaign focus on Jewish philathropist George Soros, as well as rhetoric that used antisemitic tropes.
Board of Deputies President Marie van der Zyl met a Hungarian offiicial in February and told him Mr Orbán's attacks on Mr Soros "represent the oldest antisemitic tropes and this has to stop".
Hannah Weisfeld, head of Yachad UK, tweeted Yair Netanyahu's tweets showed "something is truly broken between Israel and the Diaspora".
Yair Netanyahu was suspended from Facebook for 24 hours in December for calling for Palestinians to be expelled from Israel.
In September 2017, he was criticised for tweeting an image that suggested his family was the victim of a conspiracy over bribery and fraud charges and used antisemitic imagery.