Significantly fewer EU citizens are registering for national insurance numbers in Calderdale than at the time of the Brexit vote, figures reveal.
Oxford University's Migration Observatory said the falling value of the pound and political uncertainty are likely factors behind the drop in numbers.
Department for Work and Pensions statistics show that just 207 adults from EU countries registered for NI numbers in the year to June.
They are required by foreign nationals if they want to work or claim benefits in the UK.
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In the 12 months to June 2016, the month of the referendum, 332 people registered.
The drop reflects the trend across the UK, where NI allocations to people from the 27 other member states went down by 29 per cent, to around 448,000.
Madeleine Sumption, director of Oxford University's Migration Observatory, said: “The sharp fall in EU migration since the referendum is likely to result from some combination of the falling value of the pound, political uncertainty and an improving economic outlook in EU countries of origin.”
The fall in EU registrations for NI numbers in Calderdale contributed to an overall decline in overseas nationals seeking to work or claim benefits in the area.
In the year to June, there were 636 registrations in Calderdale, compared to 678 in the 12 months to June 2016.
This also reflects the national picture – around 706,000 NI numbers were handed out in the year to June, 14 per cent fewer than three years earlier.
Over the same time frame, non-EU registrations increased 32 per cent to about 256,000.
The non-EU region with the highest number of registrations in Calderdale was South Asia – 274 people were handed an NI number.
Ms Sumption said non-EU migrants tend to do more skilled jobs than EU workers, because it is difficult for them to get visas for low-paid work.
She added: “One consequence of the recent shift in where migrants are coming from is likely to be a slower growth in the number of migrants in low and middle-skilled jobs.”
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The DWP says the figures should not be used to indicate immigration levels, as foreign nationals could have been in the country for some time before applying.
The statistics include students working part-time, and include all workers regardless of their length of stay in the UK.
A DWP spokesperson said: “We want everyone already in the country who can continue contributing to our jobs boom to do so, wherever they’ve come from.
“The Prime Minister has set out this Government’s ambitious vision for a future immigration system that prioritises skills from around the world and welcomes talented and hard-working people to study, work, visit and do business in the UK, while taking back control of our borders through bringing freedom of movement as it currently stands to an end.”