Cohanim have been advised not to take El Al flights to Israel from Heathrow to avoid the risk of ritual contamination from bodies being transported for burial.

The Vaad Mishmeres Hakohanim, a group which protects the purity of Cohanim, has published advice on potentially problematic flights following queries from the public.

According to Jewish law, descendants of the ancient priesthood are forbidden to come near a corpse except in the case of specified close relatives.

El Al flights from Gatwick, Stansted and Luton do not transfer bodies for burial in Israel; neither does British Airways from Heathrow.

But around 10 per cent of El Al flights from Heathrow carry a body.

Since it was usually only possible to confirm whether a body would be on board a few hours before departure, the Vaad advised Cohanim to avoid any flights where there was the possibility of a body being transferred.

Vaad member Eli Katz said most transfers took place on night flights.

Priestly purity was "one of the most complex" areas of Jewish law, he said, which is why there were "different valid halachic opinions".