Boris Johnson has been urged not to let the International Criminal Court’s controversial announcement of an investigation into alleged war crimes by Israel go unchallenged.

In a letter to Prime Minister, the Conservative Friends of Israel group also labelled this week’s confirmation of the ICC’s decision by the outgoing Prosecutor Fatou Bensouda a threat to UK interests.

CFI’s Parliamentary Chairmen, Rt. Hon. Stephen Crabb MP and Rt. Hon. The Lord Pickles and Honorary President Lord Polak wrote that the  “dangerous precedent” raises the possibility that non-state actors will be able to “pursue vexatious claims against [the UK] and our brave armed forces”.

The letter emphasised that: “In our [the UK] own interests, we cannot afford to allow this to go unchallenged”.

Recognising that the UK government “rightly speaks about the need for reform of the ICC”, the letter calls for the UK to “now go one step further” and condemn the decision.

In Wednesday’s letter, the CFI officials said: “This ruling was made contrary to settled international legal principles, and was predicated upon non-binding United Nations General Assembly Resolutions.

“It should worry us all that this decision now risks rewarding and emboldening those that wish to harm the Middle East Peace Process, including Palestinian terror groups.

“The government rightly speaks about the need for reform of the ICC, but it must now go one step further.

“We should stand by our close ally and friend Israel and call out this investigation which sets both a dangerous precedent for non-state actors to pursue vexatious claims against this country and our brave armed forces, but also stands to severely affect the UK’s own sovereign legal determinations.

“In our own interests, we cannot afford to allow this to go unchallenged.”