White Britons are increasingly moving from London boroughs with large ethnic minority populations, a report from an immigration-monitoring group says.
Many city schools are multi-racial
Migrationwatch UK says the growth of some areas which are largely black and Asian is causing integration problems.
The study draws mainly on data from the 1991 and 2001 censuses and figures from the Office for National Statistics.
Immigrants' groups said the report was "unhelpful", and questioned the way the statistics were interpreted.
"The Migrationwatch figures are not helpful to a good climate of race relations and we question the analysis," said Rhian Beynon, of the Joint Council for the Welfare of Immigrants.
She said people left urban centres for "all sorts of reasons", and added the reasons why people from certain groups lived together were also "complex".
"Where you find clusters of ethnic groups living together this may be because certain groups have experienced racism or poverty and are living close to traditional industries they've worked in," she said.
During the period 1993-2002, more than 600,000 more people moved out of London than came to it from elsewhere in the UK, the report says.
It also says 726,000 immigrants arrived in the capital.
"As international immigration into London and the South East has increased, so the outward migration of Londoners to other regions of the UK has accelerated," said Sir Andrew Green, chairman of Migrationwatch.
'Stress on services'
Migration from London was highest in areas with the largest ethnic minority populations such as Brent and Newham.
In these areas, ethnic minorities had become the majority between 1991 and 2001, the report said.
White population of Newham
1991: 58% of total
2001: 41% of total
Source: National censuses
For example, 58% of Newham's population was white in 1991, compared with just 41% in 2001.
In Brent, the white population fell from 58% of the borough's total population in 1991 to 46% in 2001.
The report says that in contrast, internal UK migration both in and out of the London borough of Havering is "practically in balance".
The borough remained predominantly white (96%) in 2001 - just a small decrease from 1991 when it was "about 97% white", the report says.
Migrationwatch says the increasing concentration of ethnic minorities in some areas is creating specific difficulties both for London boroughs and areas of the UK where Londoners are moving.
"It places enormous stress on housing, education, health and social services in immigrant areas while at the same time the South West, South East and East Midlands are having to expand facilities rapidly to cater for the outflow from London," Sir Andrew said.
'People will move'
Families with young children were the most likely to move out of London, Migrationwatch said, with anecdotal evidence suggestion education was one reason for this.
The ONS' internal migration statistics are not broken down by race and immigrants' groups say Migrationwatch is reading a great deal into the figures in terms of exactly who is leaving London.
"Migrationwatch are past masters at taking a few inadequate statistics from the Home Office and then extrapolating them into the stratosphere," said Keith Best of the Immigration Advisory Service, an independent charity.
"Migrationwatch have an agenda which is anti-immigration so I'm not surprised to find them using every argument however spurious in support of their anti-immigration stance.
"I don't think this study adds one iota to the immigration debate. People will move and so what?," Mr Best added.