Over a million people in Britain are not speaking English at all or very well due to mass immigration over the past few decades.
According to figures from the 2011 Census, half of people in some parts of the UK admitted to being unable to speak English at all or not very well.
The country's most diverse areas are all in London, official statistics show. But they lay bare the vast differences in the country's ethnic map - with some areas having less than one per cent speaking a foreign mother tongue, reports The Sun.
Most mixed is Newham, East London, where just 59 per cent use English as their main lingo. Next is Brent, in the capital's north-west, with 63 per cent native English speakers, according to the Office for National Statistics.
Outside London, the two most diverse cities are Leicester, where only 72.5 per cent speak mainly English, and Slough, Berks, where 73 per cent do.
In contrast, Redcar and Cleveland is the country's least multicultural area, with English the main lingo for 99.3 per cent.
North-East Derbyshire, Staffordshire Moorlands and Caerphilly in South Wales also have more than 99 per cent in the same bracket.
In London one in four people did not speak English as their main language, with that figure rising to 4.2m across the whole of the UK.
Across the country 138,000 people could not speak English at all.
The shocking numbers reflect the hundred of thousands of Eastern Europe workers who have moved to Britain since the EU expansion in 2004.
Sarah Mulley, of left-wing think-tank the IPPR, said that speaking English is essential in everyday life. It's legitimate to expect anyone who wants to make a life here to learn the language. Many migrants have to speak English before they come and almost all are keen to learn, she added.