British communities are becoming divided along racial lines, creating a "fertile breeding ground for extremists", the head of the Commission for Racial Equality said on Thursday.
Trevor Phillips said Britain faced the danger of becoming a segregated society with divisions similar to those seen in New Orleans after the devastation brought by Hurricane Katrina.
"What we're discovering is as a country we're not talking across the ethnic, religious and colour lines," Phillips told BBC radio. "Research ... shows there's more residential segregation - we're reaching US levels now."
Many saw racial divisions in the United States exposed by Hurricane Katrina, where the overwhelming majority of people trapped in the wreckage of New Orleans were poor blacks.
Phillips warns Britain could also see ghettos emerging in cities unless more was done to encourage racial mixing. Schools were becoming more segregated, with children not making friends across the colour line, he said.
Community divisions were brought into focus by the July 7 suicide bombings in London carried out by four British Muslims. Three of the four men came from the same ethnic Pakistani community in northern England.
Phillips said Britons could enjoy a peaceful coexistence when life was calm. But communities would turn on each other in "moments of stress" such as natural disasters or recessions.
"Young people are more likely to have exclusive circles of friends than older people. Our worry is this is fertile breeding ground for extremists," he said.