Migrationwatch said the scheme, administered by the Home Office, flies in the face of government figures which show that more than 40 percent of young Bangladeshis already in Britain were unemployed.

According to the 2001 national census, there were just under 25,000 Bangladeshi men aged 16 to 24 in the United Kingdom, of whom 10,000 were unemployed, the conservative think-tank said.

"It is incomprehensible that when there are large numbers of young Bangladeshis already here who are unemployed it should be thought necessary to issue work permits to many thousands more," its chairman Sir Andrew Green said.

"Surely the people already here should be offered these jobs, or should be trained to do them, before we add still further to immigration. It simply defies logic."

The Home Office's "sector-based scheme" allows unskilled immigrants to come to Britain for up to a year, to fill vacancies in industries with jobs available such as agriculture and hospitality.

A Home Office spokeswoman in London said the scheme was led by employers' need for workers.

"It only allows people into the UK who will contribute by filling vacancies which can't be taken by resident workers," she said.

"The number of low-skilled workers allowed into the UK from outside the European Union remains small compared with other countries and is controlled by strict quotas which have been further reduced" since EU enlargement on May 1.