Bees play a crucial role in agriculture because they pollinate crops. But last year an average of 19.2 per cent of colonies died out over the winter, double to acceptable level.
The experts, who are calling for more money to be devoted to research, said the highest losses were in the north of England, where 32.1 per cent died.
The situation is thought to have several causes, including viruses, a parasitic mite, and changes in the weather.