Historian Andrew Roberts has launched a scathing attack on British policy towards Israel, claiming only Israel itself is prepared to defend Jews from a second Holocaust.

Speaking at the Anglo-Israel Association’s annual dinner in London on Tuesday, Mr Roberts pledged to “strip away some of the myths” surrounding the relationship between the two countries.

The author said Britain had never been “much more than a fair-weather friend to Jewish national aspirations”, and concluded: “In her hopes of averting the threat of a second Holocaust, only Israel can be relied upon to act decisively in the best interests of the Jews.”

Mr Roberts, whose books include studies of Hitler and Churchill, said the Foreign Office was “implicitly racist” and to blame for the fact no member of the Royal Family has visited Israel on an official visit.

He said an “unwritten and unacknowledged” ban on official visits acted as a delegitimisation of Israel and was as serious as academic boycotts and was the “direct fault of Foreign Office Arabists”.

President Barack Obama was also criticised for being the “least pro-Israeli president since Eisenhower”.