How immigration has caused problem after problem for Tory prime ministers

Immigration policy has proved a double-edged sword for the Conservatives in recent years.

Ramping up rhetoric against migrants has won the Tories votes at times but at other points it has alienated swathes of the public, annoyed business leaders and caused the party to tie itself in knots.

David Cameron promised to keep net migration to the “tens of thousands” during the coalition years, partly toughening his rhetoric to neutralise the advance of Nigel Farage’s Ukip.

This target – which has never been met – would become a millstone for the party. Despite the government’s promises, in March 2015, net migration hit 330,000.

Theresa May, fresh from the Home Office where she took the hardest line in the cabinet on immigration, maintained dogged support for the target on entering Downing Street in 2016.

But towards the end of her premiership it became abundantly clear that she was isolated over her support for keeping the threshold.

May assumed that Brexit voters wanted a hardline stance on immigration, so her red lines included an end to freedom of movement – torpedoing any hopes of the UK retaining access to the single market.

Tough talk on immigration may have appeased some voters but it worried businesses and public services such as the NHS, which relies heavily on staff from the EU.

May’s insistence on perpetuating a “hostile environment” for illegal immigrants also had a significant human cost, resulting in a damaging row over the treatment of the Windrush generation.

Boris Johnson, now ensconced in No 10, is braced for his own battles over immigration.

One of his main election promises was to deliver an Australian-style points-based system when the UK leaves the EU, continuing with the idea that Brexit was a cry to take back control of Britain’s borders.

But the plans for such a system – based on factors such as age, qualifications and previous study in the UK – have already been criticised by the government’s own independent advisers.

The Migration Advisory Committee chair, Professor Alan Manning, described Johnson’s promises as a “soundbite” and urged him not to repeat the “mistakes” of earlier attempts to impose a points system more widely.

The independent expert panel also backed a minimum salary level for new arrivals of £25,600 a year – a decrease from the £30,000 proposed during May’s premiership.

However this is unlikely to appease employers seeking skilled but low-paid staff, such as care workers and lab technicians. The social care sector, which is already under immense strain, would be hit particularly hard.

Johnson could have a row on his hands that even an 80-strong majority won’t solve. Eye-catching electoral promises can be hard to implement and he will need to be cautious of following May in keeping targets he cannot meet.

And all the while the clock is ticking towards the end of the Brexit transition period in December, when free movement for EU nationals ends and a new system must be ready to go.