Prime Minister Boris Johnson has unexpectedly stepped into the debate about whether the International Criminal Court should investigate alleged war crimes by Israel — and firmly announced his opposition to such an investigation.

n a letter released last night to Conservative Friends of Israel leaders Lord Polak, Lord Pickles, and Stephen Crabb MP, Mr Johnson said: “We oppose the ICC’s investigation into war crimes in Palestine”.

This, he said, was because Britain “did not accept that the ICC has jurisdiction in this instance, given that Israel is not a party to the Statute of Rome and Palestine is not a sovereign state”.

He added: “This investigation gives the impression of being a partial and prejudicial attack on a friend and ally of the UK’s”.

The prime minister’s intervention comes after the CFI leadership raised the issue with him and Foreign Secretary Dominic Raab in both letters and meetings.

In response to Mr Johnson’s letter, Lord Polak, Lord Pickles and Mr Crabb said:“We strongly welcome the Prime Minister's confirmation of the UK’s opposition to the ICC’s controversial investigation. The investigation has rightly been condemned for giving ‘the impression of being a partial and prejudicial attack on a friend and ally’. As the Prime Minister states, the ICC does not have jurisdiction and we support the UK's decision to stand with Israel against the probe”.

Britain is a founder member of the ICC, as Mr Johnson made clear in his letter to the Conservative Friends of Israel, and thus speaks with authority in the matter.