Diaspora Jews should be prepared to demonstrate if the new Israeli government were to implement some of the plans in its coalition agreement, the vice-chairman of the World Zionist Organisation warned.

Yizhar Hess, who represents Mercaz, the Masorti movement, at the WZO, said “unprecedented steps” may be necessary if the government changes the Law of Return - which grants diaspora Jews the right to emigrate to Israel - or allows the Knesset to override Supreme Court rulings.

“I think we are not there yet,” he told the JC. “But I do think that this coming government - that was elected democratically by the citizens of Israel - might change some core fundamentals vis a vis the soul of the state of Israel and its democratic principle.”

Some of Prime Minister Benjamin Netanyahu’s allies want to restrict the Law of Return, removing its current applicability to the grandchild of someone Jewish.

Amending the law would change “one of the essences of Zionism”, he said.

“I think it is important enough for all of us to demonstrate against it, in Israel and outside.

“If the stature of the Supreme Court is changed and, God forbid, things that happened in Poland or in Hungary will happen in Israel, this is a point in our history where a cry-out-loud voice should be going to the streets, without violence, in a respectful way and out of love, Sometimes you cry out loud out of love.

“This is how I feel today about my beloved Israel. This is how many of the Jews I met outside Israel feel about our beloved country.”

Dr Hess was in the UK this week for the Limmud Festival, where he gave lectures on the 125th anniversary of the First Zionist Congress in Basel and on state and religion in modern Israel.

Herzl had wanted to hold the Zionist movement's inaugural event in Munich rather than Basel - but rabbis from across the religious spectrum in the German city had been opposed to his project to found a Jewish state, Dr Hess explained.

The WZO’s Limmud delegation also hosted the UK premiere of a one-man show about one of America’s most prominent rabbis in the 20th century, Abraham Joshua Heschel, who was both a Zionist and social activist as well as one of contemporary Judaism’s leading thinkers.

Dr Hess told the JC he was “proud” of the Board of Deputies for having told the ultra-nationalist politician Bezalel Smotrich, who is now a minister in the new government, to go home when he visited the UK earlier this year.