London, March 18 (IANS) A 'deepening tide of tolerance' over half a century has created the grounds for Britain to elect its first black prime minister, according to a new book tracking public attitudes in Britain and the US.

Unfortunately for the aspiring British Obama, the authors don't see it happening anytime soon.

'Age of Obama', published this week as a major collaboration between Harvard and Manchester universities, draws its conclusion on the strength of survey data tracking 50 years of attitudes on issues such as mixed marriages, working for a black boss and voting for non-white politicians.

The data shows that racial prejudice in Britain and America has been declining over the past 50 years - thanks to the greater tolerance of younger generations - say authors Harvard professor Robert Putnam, Manchester professor Ed Fieldhouse and British journalist Tom Clark.

'Despite the continuing racial divides in America, we have seen how a slow and deepening tide of tolerance made possible the election of a black President a little over a year ago,' said Putnam.

'In addition, a new generation of black politicians in America - that goes well beyond Barack Obama - has emerged, and is starting to seize the opportunities this change presents.'

'As we approach the UK general election, the minimal representation of non-whites in the House of Commons and in local government will clearly continue to be a significant bar to the arrival of a British Obama.'

'But the most obvious question for the British is whether the Obama phenomenon could happen in the UK.'

Despite caveats - especially the small number of black British politicians - the answer, according to the authors, is yes.

In the run-up to the British election due by June 3 - the likely date is reported to be May 6 - several MPs have been campaigning for steps to increase the number of Black and Asian members of parliament.

They want Britain's main political parties - Labour, Conservatives and the Liberal Democrats - to reserve seats for ethnic minority candidates in electable seats, just as Labour did for women at the 1997 election that returned a record 121 women to parliament.

The British parliament has only around 15 black and ethnic minority MPs out of a total of 646, whereas it will need at least 58 to reflect the general demographic profile of the country.

However, positive discrimination is illegal in Britain, a problem that former prime minister Tony Blair got around in 1997 by striking an informal agreement for all-women shortlists.

Co-author Fieldhouse added: 'The good news is that in terms of the underlying attitudes of the majority, Britain is becoming more tolerant, just as they are in the United States.'

The book also says that though black-white racial disparities appear to be greater in the US than in Britain, probably because of the long legacy of slavery, the US is better than Britain at integrating new immigrants, probably because of America's experience as 'a nation of immigrants'.