Population - Sizing Illegal Immigrants

Claims of over 2 million Muslims in 2001 have little or no evidential basis.

Despite its importance as an official, robust information source, there is still a lack of clarity as to what the census contains, even within policy and administrative offices. The census is like a ‘macro photograph’ or frozen position of the UK on a certain day, usually a Sunday (Sunday, 29th April 2001 or Sunday, 27th March 2011), rather like a giant collection of photographs of all homes and dwellings at a particular point in time. It will, for example, capture visitors in a house. Its scope covers communal places and, in theory, its count encompasses illegal immigrants. But it cannot be considered a reliable method to capture the UK’s illegal population, and consequently, this can affect public and political opinion as to how accurately the census is reflecting the UK population as a whole.

The questions and suspicions over Britain’s illegal population impacts upon the question of Britain’s Muslims more acutely, given its topical importance. The Home Office’s Research Development and Statistics Directorate report of 2005: Sizing the unauthorised (illegal) migrant population in the United Kingdom, can provide us with research to approach the census count of 1.6 million, but this is essentially a matter of estimating what proportion of the illegal population found in the report are Muslims and how many of those are already captured by the census – in both cases we do not know. This illegal population is broadly made up of illegal and fraudulent entrants, people who ‘overstay’ their legal visas and asylum seekers who are not permitted to stay and have exhausted their rights of appeal.

Sizing is based upon on legal ethnic and migrant populations already present.

There is currently no devised method used to count the UK’s illegal population, and different methods are used by different nation states. The report adopts the official US ‘Residual Method’ and estimates that in April 2001 the UK had an illegal population of 430,000, equal to 0.7% of its true population. The report provided this figure of 430,000 as a central estimate between an estimated range of 310,000 at the lower end to 570,000 at the upper end.

This estimate of 430,000 cannot reliably be broken down into religious groups to provide sub-estimations, and is built upon ethnic and migrant populations present and the flow of persons to and from countries. What this does mean is that the proportion of Muslims within the estimates would be significantly higher than the proportion of Muslims against the population.

Muslims make up 2.8% of the population of Great Britain but would constitute more than 2.8% of the illegal persons count. These factors can mean that the 1.6 million count is lower than the actual, but there is little credible ground to state the UK Muslim population greatly exceeded that count in 2001, beyond an often used population figure of 2 million.

The Home Office estimates illegal immigrants make up 0.7% of our true population
© Crown Copyright. Source data has been derived from ONS Census 2001, unless otherwise stated.