GETTY The ONS has been urged to tell the truth about levels of migration

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The UK Statistics Authority has told the ONS, a Government department, there is "speculation about the quality" of migration figures. The public must be told if official data "falls sort of providing a picture" about the number of migrants in the UK, an UKSA spokesman said. Recent ONS figures about EU migrants have differed from data released by the Department of Work and Pensions.

In a letter sent last week, Ed Humpherson of the UKSA highlighted "the lack of a clear explanation of the differences between the DWP and ONS figures". Failing to address this could "undermine public confidence in official migration estimates", Mr Humpherson said. He added: "It is also important that the strengths and limitations of all the data sources are well explained."

GETTY The row comes ahead of the EU referendum on June 23

Sorting this out must surely be the top priority for the ONS Lord Green of Deddington

Lord Green of Deddington, chairman of Migration Watch, last night said Mr Humpherson's letter was "a very significant development". He added: "At issue is whether immigration has, in fact, been significantly higher in recent years than the official immigration figures have suggested. "Sorting this out must surely be the top priority for the ONS in the period before the referendum."

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