Trevor Phillips, head of the Commission for Racial Equality (CRE), is getting a reputation for challenging cosy progressive assumptions about British society. Last year he attacked the “lazy” philosophy of multiculturalism, which “begins by defining people as different and then treats them differently”. The result of this politically correct strategy, foisted on the country by well meaning but misguided liberals, is that Britain has a rich diversity of peoples who fail to connect.

Now he has taken his argument further. Britain, he will argue in a speech this week, is far from the melting pot we sometimes like to believe. Most people cannot name a single friend from another race. Even in London, where a third of the population is black or Asian, most whites have no non-white friends. This “soft” segregation, he says, suggests that Britain is moving towards being a segregated, ghettoised society. We looked with horror at the plight of poor blacks in New Orleans and wondered how America could have become such a divided society. But put a mirror to our own society and it is not much more flattering.

“The fact is that we are a society which, almost without noticing it, is becoming more divided by race and religion,” he will say. “We are becoming more unequal by ethnicity. Our schools — and I mean the ordinary schools, not faith schools — are becoming more exclusive and our universities are starting to become colour-coded.” Young people from ethnic minorities are increasingly born, brought up and educated in enclaves.

A study last month for the Royal Geographical Society showed the proportion of Asians living in such enclaves was up by 30% in a decade and listed eight cities, including Leicester, Birmingham and Bradford, where levels of ethnic segregation were beginning to approach those of some American cities. In Bradford, according to Mr Phillips, the proportion of Pakistanis (or children born to Pakistani parents) living in “ghetto communities” trebled in the 1990s. A Sheffield University analysis showed that in Wembley, north London, more than 50% of the population was born abroad.

This is not what was envisaged. While first- generation immigrants may have been hampered by lack of money and an inadequate grasp of English, it was believed that their children would integrate into society. It had happened with earlier generations of immigrants and to a significant degree among the generally successful Indian population. But it is not happening for Pakistanis or, more recently, the Bangladeshis; in Tower Hamlets, east London, many primary schools have more than 90% Bangladeshi pupils.This is not just a problem for what Mr Phillips describes as the “marooned communities” away from the mainstream. A society that is divided fails to achieve its potential. It is also dangerous, fostering racial intolerance, riots and, as we saw in July, terrorism. Security against terrorist attack and integration go hand in hand.

What should be done? It is vital to focus on shared British values built around the English language. That does not mean ignoring or sweeping away differences. It does mean placing obligations on everybody to communicate in the same language. Reports produced by the mayor of London are routinely available in Arabic, Bengali, Chinese, Greek, Gujarati, Hindi, Punjabi, Turkish, Urdu and Vietnamese. Councils produce documents in as many as 30 different languages. The danger is that they preserve the language differences which reinforce segregation.

There is much else that can be done. Schools and workplaces should be more integrated, although this is not easy. Arranged marriages should be discouraged. Ethnic minorities have to be convinced that they can succeed in Britain with hard work and enterprise, opportunities that are non-existent in some communities. Above all, we need to bring about a new unity around common values. It may be our biggest challenge.