Theresa May's disastrous immigration targets pushed the UK into an uncertain Brexit – things are set to get much worse

The PM has built her political career on a dogged determination to cut immigration. Judged by her own standards, she has failed

The Home Office’s infamous 'Go Home' vans circulated around the country under Theresa May’s tenure (PA)

In much the same way as the assassination of Archduke Ferdinand was the trigger, if not the underlying cause, of the First World War, the adoption by the Conservatives of an unattainable immigration target triggered the demands for tighter control of EU immigration which is leading not merely to Brexit but to extreme forms of exit by leaving the single market.

I don’t know whether the Conservative pledge in 2010 to cut immigration to the tens of thousands was dreamt up in the bath by David Cameron or, more likely, was inserted in their manifesto by some obscure adviser with nobody understanding its significance. Either way there have been serious consequences which were clearly not understood by those in search of a crunchy soundbite to fight an election. The figure seems to have been plucked out of the air with no evidence base and with no realistic prospect of meeting it. The most damaging consequence of choosing a target in this amateurish and arbitrary way, and then hopelessly missing it year after year, has been a deepening public cynicism feeding the narrative that immigration is “out of control”.

Theresa May has built her political career on a dogged determination to cut immigration. Judged by her own standards, she has failed. As Home Secretary she sent out vans decked with posters telling immigrants to “go home”. And as Prime Minister she has refused to give an unqualified guarantee to remain for EU citizens already here, preferring to use them as bargaining chips in her bigger Brexit negotiation. But despite all this posturing, immigration has not gone down. Meanwhile, she has caused real anguish. These are real people, with real lives, who have also contributed much to Britain’s society and economy. That is why I am such a strong supporter of The Independent’s campaign, Drop the Target – a target which has no remaining credibility.

“Net immigration” is a number which subsumes several other numbers which have different origins and mean different things. The most obvious groups are workers from outside the EU on Tier 2 visas; dependents and spouses of non-EU migrants; EU migrants exercising their right to live and work in another EU state; refugees and asylum seekers who are admitted under a separate legal regime; British people who are returning from periods overseas as expatriates; British people who emigrate (the fewer who emigrate, the higher net migration is); and overseas students who are not immigrants but are caught in the definition if they stay for over a year.

The case of overseas students illustrates the absurdity of the target and the malign consequences of it. The vast majority of students return home – apart from a few who have special skills and are recruited for post-study work, and some others who illegally overstay. The problem is that we don’t know how many overstay because the Border Agency did not, until recently, count people out as it counts people in. It operates on guesswork and on the basis of an airport survey which is laughably inaccurate and wildly exaggerates the numbers of over-stayers. Liberal Democrats in government sought to institute exit checks but a combination of Treasury cuts, incompetence and lack of backing from the then Home Secretary led to endless delays.

Instead, the wrongly estimated numbers of net migrants in the form of overseas students inflated the overall numbers and fuelled the immigration panic. There was undoubtedly some abuse and some bogus colleges, but on the assumption that enormous numbers of students were here illegally and that universities and colleges were complicit in these scams, the Home Office cracked down on overseas students in general. My Department of Business stopped the more draconian controls but large numbers, especially from India, have been deterred from coming here and go to the USA, Canada and Australia instead, depriving British universities and colleges of income and British firms of access to expensively trained engineers and scientists who are forced to leave after graduation.

The courts have ruled that 48,000 overseas students have wrongly, and illegally, been sent home without completing their courses, in some cases sacrificing a lifetime of earnings and borrowings by a poor family. One of Britain’s most successful export industries – higher education – was, and is, being sacrificed by Theresa May’s Home Office in pursuit of the immigration target.

The economic damage caused by the preoccupation with an immigration target goes much further than the specifics of overseas students. The economics of immigration is not totally straightforward since the additional economic activity immigrants generate is not necessarily an increase in per-capita income. There are also social pressures on the supply of accommodation. But generally, the immigration of young people who come to work in occupations which face a skill shortage, or labour shortage more generally, adds significantly to national economic welfare. Conversely, a crackdown to meet the target will undermine economic welfare.

A relatively large net inflow of workers is both a consequence and a cause of economic growth. A big cut in net migration as government policy currently demands will inevitably follow the slowdown which Brexit will bring since there will be less demand for overseas labour and more British people emigrating, looking for work. But attempts to curb recruitment overseas to meet the target will, in itself, lead to economic slowdown as production is disrupted.

Of course we should be training more British people to do jobs with scarce skills but this requires a more considered, longer-term, approach than the pursuit of arbitrary, politically driven targets.

Sir Vince Cable is leader of the Liberal Democrats and was Business Secretary from 2010-15

Please sign our petition to call on the Government to Drop The Target: