The UK's Office for National Statistics (ONS) says that by using improved methods, it has discovered that certain statistical information about net migration to Britain in 2023 and 2024 needed to be revised and adjusted to reflect actual migration numbers.

Net migration is the difference between the number of people arriving in a place for a long stay and the number leaving the country to live elsewhere for a prolonged period.

The improved methods show higher emigration by British nationals, bringing overall net migration figures slightly down.

According to the new methods employed by ONS, net migration in the UK hit its peak several months earlier in 2023 than previously assumed, with 944,000 people reaching the UK in the year ending March 2023 — as opposed to the previous estimate of 906,000 people coming in the year ending June 2023.

In 2024, on the other hand, there was a sharper fall in numbers than had initially been reported, with net migration in the year ending December 2024 now readjusted to 345,000, which is significantly lower than the original estimate of 431,000 published by the ONS six months ago.

In 2022, record immigration numbers in the UK galvanized a growing anti-migrant sentiment across the political spectrum, which persists to this day.

Read AlsoUK immigration nearly triples despite Brexit promises

'Uncertainties remain' despite improvements

The improved methods in determining these net migration figures mainly focus on the movement and migration of British nationals away from the UK.

The new methods used for estimates on net migration are now produced by using data from the Department for Work And Pensions, which the British Press Association (PA) news agency referred to as "more robust and comprehensive."

This estimate incorporates everyone with a national insurance number — which is Britain's social security and tax administration system. 

By using this method, ONS can more easily determine the likely migration status of UK individuals, based on their tax contributions — or lack thereof.

Georgina Sturge, a research affiliate at Oxford University's Migration Observatory, said the new method would "almost certainly" provide a more accurate picture of migration, adding however that "uncertainties remain."

"The method for estimating the migration of British citizens is very much experimental and future revisions are likely," she said.

Read AlsoUK sees sharp drop in work visas as asylum claims reach record high

More Britons leaving than previously believed

Estimates for the net migration of British nationals had previously been based on the International Passenger Survey (IPS) used in the UK, which provides only a small sample size according to PA.

ONS said that this system had been "stretched beyond its original purpose," and therefore was no longer considered to be a reliable measure.

Mary Gregory, the director of population statistics at ONS, said that for several years, new ways of exploring and analyzing data had been under ongoing revision following a Census 2021 in the UK, which apparently showed the IPS system was considerably underestimating the number of British people living and moving abroad.

"Understanding the long-term international migration patterns of British nationals has been, and always will be, challenging due to the sheer number of British people crossing the border on a daily basis," she told reporters, adding that "(v)ery few of these will be migrants."

Read AlsoNet migration to the UK halves in 2024 after fewer study and work visas issued

EU+ immigration variations persist

At the same time, the ONS reports that improvements have also been made in the way that it estimates the nationals to the UK from the EU+ countries, which covers the 27 member states of the European Union plus the nations of Iceland, Liechtenstein, Norway, and Switzerland.

"Based on these new data and methods, it is clear the IPS continued to underestimate … immigration" from EU+ countries in recent years, Gregory added.

Part of the influx in EU+ arrivals to the UK in recent years could potentially be linked to the UK's departure from the European Union, commonly referred to as "Brexit," which gave EU nationals a grace period of several years to still enter the UK and settle there. 

Struge however added that among the challenges that remain in determining net migration numbers in the context of EU+ citizens coming to Britain in recent years, "there is still no good method for taking into account EU and non-EU visa overstayers."

Read AlsoUK government presents tougher migration measures to parliament

with dpa