Blunder hides true scale of migration into UK

The mistake was discovered by the Office for National Statistics (ONS) in May when it compared the results of the 2011 Census with the population it had expected to find on the basis of births, deaths and official immigration figures, campaign group Migrationwatch UK said.

Immigration between mid 1997 and mid 2010 now totals nearly four million, rather than the 3.4 million recorded.

News of the miscalculation came as police revealed 15 asylum seekers had been found in a tanker on a cross-Channel ferry at the Port of Dover.

Two of the migrants, who were on P&O’s Spirit of France on Tuesday, were taken to hospital though neither was in a life-threatening condition. Police said two drivers were taken into custody.

Migrationwatch UK has written to the UK Statistics Authority watchdog to insist the ONS revises the official numbers – something the group claims it has refused to do.

Sir Andrew Green, chairman of Migrationwatch UK, said: “For the sake of public confidence in government statistics there must be a thorough revision of the immigration statistics and the new figures must be published without delay.”

Migrationwatch UK added that allowing for the one million British citizens who emigrated between 1997 and 2010, net immigration comes to three million.

ONS spokesman Paul Vickers said: “It is simply not true to suggest that ONS has ‘refused’ to revise migration estimates.

“ONS produced a revised population estimates series which incorporates the net migration findings from the 2011 Census.

“The series, going back to 2002, was published in December 2012. At the same time we announced plans to publish a report analysing the quality of the long-term international migration data since 2001, including impacts of the improvements made to the data since this period. This will be published in the autumn.”