There are two types of fraud-based denaturalisation in the United Kingdom.
The statutory power to deprive a British citizen of their status on the basis of fraud was introduced in 1914. It is unknown how frequently this statutory power was exercised in previous years but it is thought to be seldom.
A further form of fraud-based denaturalisation emerged through case law. In the 1978 case of Sultan Mahmood  QB 58, a man had adopted the identity of his dead cousin and later purported to register as a British citizen in that identity. The court held that the purported registration was a nullity because of the man’s fraudulent adoption of the identity of a real person.
Later cases expanded the circumstances in which a previous recognition or grant of citizenship might be simply disregarded in this fashion as a nullity. Statistics for both these forms of fraud-based denaturalisation are available for the period since 2012, and show a significant subsequent expansion in exercise of the power.
The rise and fall of citizenship nullification
The British state found it convenient to rely on simple declarations of nullity, challengeable only by way of an application for judicial review, rather than the statutory power, which carried procedural safeguards and a full right of appeal. The number of nullity declarations soared in 2013 from a very low base to 176 cases in a single year before subsiding again.
In 2018, the Supreme Court held in a case call Hysaj  UKSC 82 that cases subsequent to Sultan Mahmood had taken a ‘wrong turning’ and therefore that many of the subsequent nullity declarations had been unlawful. The statutory power should have been exercised instead.
The number of statutory fraud-based deprivations then began to rise then increase sharply to 273 cases in 2021. It may well be the case that a proportion of the more recent statutory deprivation decisions have been made in respect of individuals whose citizenship was previously unlawfully nullified then in effect restored by the Supreme Court judgment.
Focus on fraud
The Home Office team responsible for denaturalisation, the Status Review Unit, was created in 2012. Prior to that, a report by the Chief Inspector of Borders and Immigration recorded that no fraud-based denaturalisations at all had been processed in the years 2008 to 2012. A later inspection carried out in 2017 recorded that the entire unit consisted of 24 staff in 2017.
In March 2017, the unit was reported to have a backlog of 1,338 deprivation cases and to be processing between 12 and 23 such cases per month. The delays caused by persistent backlogs, the opportunistic, non-systematic way in which cases are referred to the team within the Home Office, the internal system of prioritisation and the availability of only snapshots of statistics on the work in progress render it impossible to link any prior migration trends with the number of denaturalisations occurring in a given year.
If you create an Inquisition, it will find heresy. Setting up a dedicated team for the specific purpose of detecting fraud is likely to lead to an increase in the detection of fraud. That does not explain why the decision was taken to devote resources to this issue, and it may be an element of circularity. The unit was set up because more fraud was noticed or suspected, and the unit then proceeded to uncover more fraud.
Morality and migrants
In practice, very few fraud-based deprivation decisions seem to lead to removal action. Those concerned almost invariably have partners and children in the United Kingdom, who are often themselves British by birth, registration or naturalisation. Indeed, the original deception is often detected only by means of the sponsoring of a family member to come to the United Kingdom.
This absence of a drastic, direct consequence to denaturalisation calls into question its purpose. In short, why devote resources to this issue — there are many arguably more pressing issues facing the contemporary Home Office — when the deception is so historic and denaturalisation will not lead to removal in any event?
Fargues argues convincingly that the British government made the need to tackle fraud one of its priorities in the field of migration, particularly but not exclusively in the context of asylum and marriage migration. The equation of migration with deception is hardly new but there is evidence to suggest that additional priority and resources have been dedicated to the issue in the context of citizenship.
The purpose of fraud-based denaturalisation appears to be a moral one. Fargues suggests the officials responsible justify their work as threatening the purpose of naturalisation, namely to celebrate citizenship as a prize available only to those deemed sufficiently worthy.
Underlying all of this is a change to the way in which value is attributed to citizenship. The once-controversial statement that citizenship is a ‘privilege not a right’ first appears in Parliamentary debates on the abortive earned citizenship legislation of 2008 and 2009. For some, the high value of citizenship means it should only be removed in exceptional circumstances, if ever. For others, the value of citizenship is enhanced by fragility. If citizenship can be broken or lost, those who hold it will cherish it all the more.
This moral dimension to citizenship is rarely stated explicitly in public but has become increasingly prevalent.
This moralistic approach is likely to lead to ever wider use of denaturalization powers, albeit primarily and disproportionately against perceived out-groups.