Politicians must urgently tackle the increasing ethnic polarisation of many of Britain’s towns and cities, according to a senior academic, as he revealed figures showing how rapidly the white British population had dwindled in urban “pockets” across England. Prof Ted Cantle, who first authored a report into community cohesion after a series of race riots in 2001, said his new study showed that in the most extreme cases the white British population had more than halved in two decades. Cantle, who co-authored the report with Prof Eric Kaufmann at Birkbeck, University of London, told the Guardian that white British families should be encouraged to remain in ethnically diverse areas to reduce the trend. He warned that segregated societies “breed intolerance and prejudice”, adding: “And we know…