Migrant populations of many towns may be thousands different than official statistics indicate, a report says.
Wrong estimates raise the risk that services get inadequate funding, the Social Market Foundation think tank claimed.
It said a major overhaul was needed and urged a greater use of data from firms like Facebook.
SMF migration researcher Jonathan Thomas said: “Our official statistics on migration and local populations are severely limited.
“Commercial data like that held by the big technology firms could help give planners a much more accurate picture of local population.”
The analysis points out that Office for National Statistics estimates of non-UK born populations in local authority areas can have large variables.
For example, the number of residents of Hastings, east Sussex, who were born overseas was estimated at 12,000 in the year to June 2018.
But a confidence interval of plus or minus 7,000 means the number may be as high as 19,000 or as low as 5,000.
The estimated non-UK born population of Boston, Lincolnshire, was 21,000, but the figure could be as much as 10,000 higher or lower.
Peterborough had an estimate of 47,000 but the number could be anywhere between 39,000 and 55,000.
This means in some towns there may be a difference higher or lower of as many as 10,000.
In some cases, the potential variation amounts to more than 10% of the entire local population, according to the report, which will be published on Wednesday.
The ONS said it will explore “alternative” data sources as part of an “ambitious programme of work” to better understand the impact of migration.