Forty-two leading figures in the British Jewish community have written an open letter to the Israeli government expressing an “unprecedented level of concern” at the prospect of unilateral annexations of tranches of the West Bank.

The letter, addressed to the outgoing Israeli Ambassador to the UK Mark Regev, claims that annexations would “pose an existential threat to the traditions of Zionism in Britain, and to Israel as we know it”.

The letter, published by Israeli daily Haaretz on Thursday, is the most outspoken criticism of the Israeli government plans for the West Bank from the British Jewish community.

Among the signatories are former Foreign Secretary Sir Malcolm Rifkind, former Labour MP Luciana Berger, Senior Reform Rabbi Laura Janner-Klausner, Senior Masorti Rabbi Jonathan Wittenberg and Times columnist Daniel Finkelstein.

Cultural heavyweights such as playwright Howard Jacobson and historians Simon Sebag Montefiore and Simon Schama also signed.

The letter says that that the concerns outlined are “shared by large numbers of the British Jewish community, including many in its current leadership, even if they choose not to express it”.  

The letter – which reiterates support for the two-state solution – skirts specific questions of Palestinian rights in any annexed territory.

“It would have grave consequences for the Palestinian people most obviously,” the letter reads, without elaborating.

The letter focusses on Israel’s “international standing” and the “notion of Israel as both a Jewish and democratic state”, both of which it says would be threatened by steps to unilaterally annex tranches of the West Bank.

The proposed Israeli annexations of the Jordan Valley and Israeli settlements in the West Bank form part of the roadmap set out by Donald Trump’s so-called peace plan, released in January.

Under the coalition agreement signed between Israeli Prime Minister Benjamin Netanyahu’s Likud and Defence Minister Benny Gantz’s Blue and White in April, the process of “extending sovereignty” to sections of the West Bank could begin as early as July 1.

The letter concludes with a warning that annexation risks endangering the relationship between Israel and the Jewish diaspora.

It says annexation would risk “polarising Jewish communities and increasing the divisive toxicity of debate within them” as well as “alienating large numbers of Diaspora Jews from engaging with Israel at all.”  

“Under these circumstances,” the letter continues, “the commitment to Israel that has been such a vital glue in sustaining and uniting Jewish communities, as well an asset for Israel, will decline.”