Despite consistently making a pledge to cut net migration to the “tens of thousands” from historic highs post-2010, it’s worth considering whether Theresa May really wants to deliver on lower net migration after all.

Firstly, it’s a target that continues to all but elude her. Net migration has held steady or risen every quarter but three since May has been either home secretary or prime minister. Last week’s new figures showing a substantial drop in net migration to 230,000 will be seen by the government as evidence their work is paying off. But, if success is reaching 100,000 or less, May is still far off with no end in sight. Instead of making promises to reach this target in the current parliament, she only claims to help move in that direction. That’s not a firm commitment to a manifesto pledge.

Secondly, May can reach the target in months if she demonstrated the political steel. Most migrants are from outside the EU where there is more control over their numbers. The government could immediately slash visas for entrepreneurs, professionals and students and reach their target in 12 months maximum. Their failure to satisfy their own pledge is not because of the European Union or a lack of control. Instead, it’s a lack of determination.

Nearly three-quarters of the net migration fall is accounted for by a drop in EU migration. Immigrants from outside Europe remain static and yet it is they – not EU citizens – that the government has firm control. Leaving the EU might help lower net migration, but the government’s target can be met regardless.

Thirdly, there is good reason to avoid hitting their net migration target in this parliament. Philip Hammond’s Budget doesn’t offer much, but it assumes continued levels of net migration paying much needed tax as the government prepares to pay for a Brexit divorce bill of £20bn or more. A larger than expected drop in net migration could damage the chancellor’s recovery plans.

Moreover, most non-EU workers are skilled professionals that may be difficult to replace without time to retrain others – putting many businesses and public services at risk with significant costs – that would have to be made up elsewhere.

Finally, it’s unclear whether reaching the net migration target – with or without the potential economic costs – will be enough to satisfy members of the public that are most concerned by border control issues, where one is one too many. I suspect that it’s not numbers, but impact, that should be the main focus. Concerns about migration numbers would lose their political heat if there was more affordable housing, better paying employment and shorter queues to visit GPs.

If I’m right, May’s promises on net migration are a poisoned chalice. Failure to meet her target becomes another campaign pledge broken or unfulfilled, but success has potentially serious costs to the economy and public services that may do little to please a concerned public. Little wonder then to see hardly any progress made – and all the more reason for the government to think more carefully about how it might address public anxieties in a way it can and wants to achieve.

There is also the growing problem that for at least three quarters in a row the only group that is leaving Britain in greater numbers than arriving are British citizens – holding steady at 49,000 less each year. A system that leads to fewer British citizens at greater costs is not a recipe for success. The status quo is unsustainable.

What should Labour do about this? Two things:

First, we should highlight Tory hypocrisy on immigration. Every time they talk about net migration providing excuses – and pointing fingers at others – for why they’ve failed to meet their targets we simply must say loud and clear that the Tories have only themselves to blame. They can reach their target now, but choose not to. This rank hypocrisy isn’t raised enough.

Secondly, we must turn attention to the real issue: impact. The reason why some want lower migration is because of concerns over impact. Reducing net migration to 100,000 will do little to address this. But focussing on impact and improving investment in public services will make a difference. Labour is right to call for introducing a migration impact fund and focusing on the core issues.

Exposing Tory hypocrisy and delivering a plan on impact can help Labour win back public confidence on immigration. The Tories have got away with too much for too long.

Thom Brooks is dean of Durham Law School.