Theresa May’s relentless obsession with the net migration target – prioritised over economic, educational, or even human rights concerns – is all the more surprising given the fact that it is such nonsense. For a number picked out of thin air prior to 2010, it is both remarkable and worrying that it became almost a sacred cow of British politics.

The net migration target (NMT) can be unpicked in many, many ways but it has been welcome to see a growing focus on the fact that a “one-size-fits-all” target for all nations and regions is just not appropriate. Clearly if the only migratory movements in the UK next year were that 900,001 people left Wales to head abroad and 1,000,000 migrants arrived looking to live in Maidenhead, this would not be good for Wales or the Prime Minister’s constituency – yet it would be the first time in eight years of trying that she had met her pet ambition.

We need to be much more sophisticated. Different parts of the UK have very different demographic and economic needs in terms of migration.

Since 2007, the Scottish National Party government at Holyrood has pursued a different population target – aiming for Scotland to match average population growth of other EU15 nations over the decade to 2017. The fact it is on course to succeed has been considerably aided by May regularly and spectacularly missing her own.

But what if May finally reduced net migration to the tens of thousands?

In 2014 the Office for National Statistics produced population projections for Scotland and the UK based on different migration scenarios. One “low net migration” scenario was 105,000 – so just outside the NMT. Even that narrow miss would see Scotland’s population almost stagnate over 25 years, barely mustering a overall population increase of 3,500 – 0.07 per cent – per year. So there is a real danger that May actually hitting or "exceeding" her target means population stagnation or even decline for Scotland. This is potentially disastrous when the population is ageing.

More generally, having migration policies in place so different geographical areas are able to attract human capital and the right labour to match skills shortages is surely in the interests of all. The UK system isn’t working well for too many parts of the UK. A very bureaucratic Tier 2 system is navigable for large companies with armies of immigration lawyers – and international firms can always rely on intra-company transfer rules. But for many small and medium-sized enterprises – a more significant part of Scotland’s economy – these are often expensive and unrealistic options, and it is no surprise that Scotland is home to fewer Tier 2 sponsors than its population size would suggest.

There is strong support for a new system, including both the Scottish Chamber of Commerce and Scottish Trade Unions Council. In the House of Commons the Scottish affairs committee, as well as the All Party Group on Social Inclusion, chaired by Chuka Umunna, have advocated bespoke immigration policies. And this week even in the House of Lords, two committees concluded there should be “maximum flexibility” for nations and regions and that there was “merit” in a specific system for Scotland (and London). Academics like Professor Jonathan Portes and think tanks such as the IPPR are supportive of the idea. But how could it be done?

With a little imagination, there are a bucket load of ways – many very helpfully set out in a recent paper by Professor Christina Boswell of the University of Edinburgh. Whether it’s applying different points thresholds for jobs in Scotland, a bespoke post-study work scheme, allowing Scotland a separate quota under the Tier 2 scheme, or a more flexible shortage occupation list, options are there which need not complicate administration or enforcement. Indeed, if there was political will at the UK level, there is no reason Scotland could not continue to allow free movement of EU nationals, which is what my party and I will continue to advocate for.

It’s worth remembering that sub-state immigration policies and autonomy work perfectly well in countries such as Canada and Australia. And the UK itself previously experimented with a post-study work visa applicable to graduates from Scottish universities (but curiously, not limited to Scottish employers) and currently there is a (very slightly) different list of shortage occupations for Scotland.

An immigration policy for Scotland is an idea whose time has come – and failure to listen could have serious consequences for Scotland’s population.

Stuart McDonald is the MP for Cumbernauld, Kilsyth and Kirkintilloch East and the SNP's immigration spokesman