Britain is facing a middle-class brain drain as professionals leave in search of better lives overseas, a report has warned.

Almost half of all Britons who emigrate each year are professionals and company managers, potentially threatening the country's supply of highly skilled workers, research for the Home Office found.

The attractions of a better lifestyle and climate, as well as career opportunities, meant a "large and increasing" number of executives, scientists, academics and doctors have chosen to leave Britain in the last 20 years, the report said.

Business leaders blamed high rates of income tax for the "disturbing" rises in the number of professionals leaving Britain for countries such as Australia, American and Canada. Around 149,000 British citizens emigrated last year, and 4.7 million now live overseas.