Leave-voting areas have seen faster relative growth in foreign workers since the Brexit referendum, a Guardian investigation has found.

Data analysis suggests that the decade since the Brexit vote may not have matched the expectations of many Leave supporters, showing their local areas have also become relatively more deprived over the same period.

Migration increased across the UK after Brexit, especially of those arriving on health and care visas, peaking at 944,000 in the year ending March 2023. Net migration has since cratered, and continues to fall as people’s visas expire.

Analysis of government Pay As You Earn data shows that between 2016 and the end of 2024, non-UK workers grew fastest in percentage terms in stronger Leave-voting areas, largely because they had previously made up a smaller share of the workforce.

Wigan, where the Makerfield byelection has taken place, follows the pattern seen in many strong Leave-voting areas. Less than 5% of payrolled employees were from outside the UK in June 2016. That had increased to just under 10% in December 2024 – more than doubling in relative terms.

Across the country, the proportion of foreign workers increased by just 40% over that period, rather than doubling.

Remain-voting areas – often larger cities – still have the largest numbers of non-UK workers. While they have seen bigger rises in absolute numbers, it is Brexit strongholds that have seen faster relative growth of their foreign workforce.

The figures highlight the fact that areas less used to migrant workers before Brexit are now seeing migration become a more noticeable part of local working life.

Anand Menon, the director of The UK in a Changing Europe and a professor of west European politics at King’s College London, said the pace of change can often be more politically salient than overall numbers.

“People react to change,” he said. “We saw this in the lead up to the referendum itself. An extra 10,000 immigrants in central London might barely register, but 200 new arrivals in Boston might be noticed.”

Separate Guardian analysis of deprivation data shows that the strongest Remain-voting seats in England, including Bristol Central, Clapham and Brixton Hill, and Cambridge, experienced the largest improvements between 2015 and 2025, while the rest of the country has stagnated or declined in relative terms.

By contrast, Brexit-voting areas such as Boston and Skegness, Hartlepool and North Warwickshire and Bedworth became relatively more deprived over the same period.

The two trends should not be mistaken for cause and effect. Many Leave-voting areas were already marked by long-running economic weakness, and wider research suggests immigration has had only very limited effects on the wages and employment prospects of UK-born workers.

The Guardian combined government deprivation data with constituency-level estimates of the 2016 referendum vote. The analysis suggests that areas with higher Leave votes have tended to fall further behind on health measures compared with Remain-voting areas, including risk of early death, more people on health related benefits, and greater hospital admissions for severe illness.

A similar pattern appears in deprivation rankings for housing and services, which measure the physical and financial accessibility of housing and local amenities. Leave voting areas have tended to improve more slowly, or worsen, compared with the rest of the country, while Remain voting areas have climbed up the leaderboards.

Changes in crime deprivation rankings, which measure how much crime is in an area compared with the rest of the country, over the past decade also show a large split by referendum vote.

Makerfield was again fairly representative. Its overall deprivation ranking slipped just seven places relative to other constituencies between 2015 and 2025. However, it fell 52 places down the housing deprivation rankings and 127 places down the crime leaderboards.

Menon warned against ascribing everything to Brexit. He said: “It’s all too easy to blame Brexit for everything that’s gone wrong in the last few years but it’s not the whole story. It was always the case that more affluent places, that have a higher skilled workforce, were more resilient.

“Given what’s happened with Covid-19, the war in Ukraine, and what’s happened to manufacturing it’s not surprising that less prosperous places, many of which voted to leave, have become relatively more deprived.

“Remainers in particular seem to have fallen into the habit of dating our economic travails to 2016. But if our economy had been functioning well then, why would a majority have backed Leave?”