A third of black and Asian people have lost out on a job because of British racism, finds a BBC survey.

The ICM poll for BBC Online found that more than half of all those questioned consider Britain a racist society and only 55 per cent believe the UK to be a more tolerant society than ten years ago.

Immigration issues also provoked a negative response, with 44 per cent believing that migration has damaged the UK over the last fifty years and two thirds of white respondents claiming immigrants do not integrate or make a positive contribution to British society.

Citizenship classes for asylum applicants received widespread support, with 78 per cent believing them to be a good idea.

Chairman of the Commission for Racial Equality Gurbux Singh considered anti-migrant prejudice to be the most worrying find of the survey.

"Britain has been collecting different cultures, skills and people for centuries. From Marks and Spencer to the Mini motorcar, some of the most famous symbols of British success have come from people who were refugees and immigrants," he said.

"We must start a new, more positive debate about immigration. Let us be clear about the benefits, and correct and shape public debate in that far more positive debate."

A Home Office spokesman said: "This is clearly a very important report and we look forward to studying it in detail."

Labour MP, Graham Allen, last Thursday wrote to Tony Blair calling on the government to promote the benefits of immigration for Britain.

The Nottingham MP cited official figures finding that "foreign-born" workers now contribute 10 per cent of UK GDP - an input "many times greater than the present contribution of North Sea oil".

"At a time when extremists (assisted by certain newspapers) are stirring up hatred against immigrants and people of minority ethnic or national origin, I think that this fact deserves to be better known," he told Downing Street.

"I wonder if the Treasury and the Home Office might do some further analysis of the economic benefits of immigration, along the following lines and to communicate the results in simple, headline language."