LONDON The national statistics office announced changes to the way it collects migration data on Tuesday just hours after the government was forced to admit it had hugely underestimated the number of immigrant workers.
Peter Hain, the work and pensions secretary, apologised to parliament on Monday after admitting there were 300,000 more foreign nationals working in Britain than official statistics suggested.
The lack of reliable data on migrant flows has been a major headache for policymakers, complicating everything from the allocation of government resources to the setting of interest rates.
Publishing an interim report into the issue, the Office for National Statistics said it would increase the sample sizes for its International Passenger Survey and consider making better use of administrative data, such as school and patient registers.
The International Passenger Survey currently samples around 0.3 percent of people entering and leaving the country at 16 airports, 21 ferry routes and the Channel Tunnel.
The ONS said extra "filter shifts" would be introduced at Manchester, Stansted and Luton airports from next April to reflect the higher number of migrants who arrived and departed from these airports in 2006.
"The ONS is engaged in a major programme to improve further the quality of its migration statistics," said National Statistician Karen Dunnell. "The International Passenger Survey is a vital source of data on this, so improving the sampling of migrants is a step forward in this very important area of our work."