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22 December 2025

Britain is blind on immigration statistics

The most important statistics in election years are more full of holes than we realise

By Ben Walker

If there were ever a set of statistics to be guaranteed front-page status in Britain, it’s the immigration statistics. How many people have come to Britain this year, net? As many as 900,000? How many Hulls a year? How many Nottinghams? Borderless Britain? Would you like to comment, Mr Farage? You get the picture.

Net numbers have been high since the millennium. The Conservative pledge of bringing net migration down to the tens of thousands was missed by a long-shot after five years in office. And Britain’s vote to leave the EU came off the backs of net migration numbers that were the highest on the record.

But what if all this is wrong? What if the numbers aren’t quite so grounded and certain as we write them up to be? The Migration Observatory has cast doubt on the numbers, with the implication being that policy made to drive migration down, be it through asylum claims, economic movement, or a showdown with the European Court of Human Rights (ECHR), may be built off the backs of gaps and, frankly, inaccurate assumptions.

Here are the main contentious. Despite an “impressive suite of immigration statistics,” the number of people living in the UK without permission is not known. The Home Office last made an projection in 2001 and has recently conceded it can’t provide a more up-to-date estimate. Assumptions about those, with visas, who leave the country before they expire are just that. The Office for National Statistics (ONS), the body behind the latest net migration statistics, is basing the net number off assumptions, assumptions that Migration Observatory claims will inevitably change as migrant behaviours change.

The number of British citizens leaving and returning is particularly uncertain. The statistics come from tax and benefit records, meaning many unaccounted for financially may be missed off the list. Those entering the UK on one passport and leaving on another may also be missed from the system. Leaving via Ireland through the Common Travel Area does not guarantee inclusion in the headline numbers.

When it comes to those claiming asylum or living illegally, we know how many have been refused asylum (that’s 138,000 as of 2024). What we don’t know is how many are still waiting on the result of an appeal (ie still living in Britain), how many have applied (and succeeded) to stay on other grounds, such as right to family life, or even how many have left the system altogether but are still living in the UK.

Now 138,000 asylum rejections does not mean 138,000 people heading to Heathrow. We simply don’t know that.

And we also don’t know the number of cases involving the ECHR. Almost four-in-ten immigration appeals bore the category of “human rights cases”, with almost 20,000 heard every year. Whether or not these cases are heard on ECHR grounds is yet to be seen. It’s not known, so talk of Britain leaving the ECHR as a sort of silver bullet solution to the asylum backlog is more stab in the dark than sure solution.

What the Migration Observatory report appreciably emphasises is whether the recent Westminster obsession with the asylum backlog is based on hard statistic, or conjecture. And the truth is there’s a lot of conjecture in the statistics we see and digest each quarter. The report rightly cautions against over-interpretation but suggests, simply, what the UK needs is more data. If it seriously wants to tackle immigration, it needs to know what type of immigration it can actually tackle. And how big a problem it is. Top-down numbers can only tell us so much.

[Further reading: How the Green party is professionalising]

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