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.