Lord Green is Chairman of MigrationWatch UK and a cross-bench peer.

This week’s immigration figures have made uncomfortable reading for a government that has pledged a major reduction in immigration. EU net migration is still, despite Brexit, at 74,000 – roughly the size of the British army. Non-EU migration is a quarter of a million – that is, the highest for 14 years.

Meanwhile, it is curious, to put it mildly, that the Prime Minister should be majoring on her achievement in bringing free movement to an end just as leaked Cabinet documents suggest that the Government is about to lose much of the benefit by caving in to the employer lobbies. They are planning, it seems, to camouflage their surrender by fiddling the immigration statistics.

The Prime Minister has indeed chosen as the top reason for backing her deal with the EU that “free movement will come to an end, once and for all, with the introduction of a new skills-based immigration system”. However, the Daily Telegraph had a leak of Cabinet papers describing how the Government proposes to manage migration post-Brexit. If broadly correct, it could well throw away much of any benefit gained from our departure from the EU.

The Government seems to have in mind fiddling the immigration statistics. They would do this by offering eleven-month visas for those wishing to work in lower skilled occupations. Presumably, this is intended to appease the employer lobbies who want continued, and preferably unlimited, access to cheap labour. The trick is this. When passengers arrive in the UK a sample are asked whether they plan to remain in the UK for a year or more. If so, they are asked further questions, and are then included in the statistics as immigrants, but if they have visas which are only valid for 11 months they will say no and walk on through.

That ruse will keep them out of the statistics but, once the eleven months are up, how could their departure possibly be enforced? A previous scheme for low skilled hospitality workers had to be closed in 2005 amidst Home Office concerns that it was being used to facilitate illegal immigration. The same could happen again with these workers joining the population of illegal immigrants who are estimated by former Home Office officials to number about one million. Alternatively, they could work legally for eleven months (probably at higher pay) and then drop off the radar. The Home Office do not remotely have the resources to find them, let alone remove them. Indeed resources devoted to border control fell by 20 per cent in the five years to April 2017.

The Government has declared its intention of treating all applicants in the same way, whether they are EU citizens or not. For those who qualify for a highly skilled work permit, this is an acceptable risk. But the apparent absence of any limit on numbers is of serious concern. The present cap of 20,700 was not reached for six years, but it has proved too inflexible over the past 18 months. A higher cap would, of course, be necessary if skilled EU workers are to be included, albeit rather more flexibly administered than in the past.

For lower skilled workers, this approach is fraught with danger. The German ‘Gastarbeiter’ system was intended to allow in temporary workers for just a year or two, but it resulted in a very large number of foreign-born workers staying permanently in Germany. Although the scheme was closed in 1973, the foreign-born population continued to increase over subsequent years as these workers brought in partners and children under ‘family reunification’. Indeed, the German government ended up offering to pay them to return to their home countries – an offer that few took up.

Labour governments have repeatedly found that changes in migration rules for work have led to major and unforeseen increases in immigration. Upon coming to power in 1997, net migration trebled in three years from 50,000 to 150,000. Later, unlike nearly all other EU member states, they decided against a seven year transition period for the admission of workers from the East European accession states. Later still, their Points Based System, introduced in 2008/9, came off the rails with tens of thousands of bogus students applying for visas in the hope of working illegally in the UK. This swamped the system in India to such a degree that several Consulates had to be closed down for a period of months.

For this not to be yet another such episode, the Government needs to be clear about who they intend to admit and very clear that they will set limits on numbers and on any rights both to benefits and to access for family members. It is vital also that the mechanisms and resources should be in place to ensure departure.

It is all very well for the Government to claim that it has restored “control” of migration but, if that leads to another increase in numbers, the outcome would be deeply unwelcome to the public, nearly two thirds of whom consider that immigration has been too high over the last decade; among Conservative voters that is 84 per cent.

The Government should be in no doubt that, especially after their stress on ending free movement, a failure to achieve a reduction in immigration will decisively affect the public’s perception of their management of Brexit.