THERESA May is urged today by MPs to “consider further" devolving immigration powers to Holyrood, warning that Scotland’s failure to keep pace with the UK's population growth could damage its future economic prospects.

What has sometimes been called Scotland’s “demographic timebomb” – a slower rate of population growth than the rest of the UK with proportionately more older people and fewer young people - is laid bare in a report by the House of Commons Scottish Affairs Committee but now comes in the uncertain context of the UK’s decision to leave the European Union.

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Nicola Sturgeon, the First Minister, has called for Holyrood to have control over migration, which was supported last month by David Watt, Scottish head of the Institute of Directors, who made clear “different measures for Scotland” needed to be considered.

However, the call has already been rebuffed by the UK Government. In October, Robert Goodwill, the Immigration Minister, told the committee: “Having a separate immigration policy for Scotland is not something that we feel would be appropriate.”

The MPs’ report notes how migration is already an important factor in Scotland’s population growth and is likely to become more so in the future.

It says: “A consequence of Scotland’s lower fertility rates is that the rate of natural population increase will be lower than other regions in the UK. To match population growth with the UK as a whole, a greater proportion of the increase will have to come through net immigration.”

The report highlights evidence from National Records Scotland, which calculated that, if current trends continued, just 10 per cent of Scotland’s projected population increase to 2039 would be from Scots while 90 per cent would be down to migration; 57 per cent from abroad and 32 per cent from across the border with the rest of the UK.

More evidence points to how many people come to Scotland in their late teens and early 20s but then a few years later leave; suggesting that this spike is due in part to free university tuition.

The report restates the committee’s call for a post-study work scheme to be introduced in Scotland to allow international higher education students graduating from Scottish further and higher education institutions “to remain in Scotland and contribute to economic activity for a defined period of time”.

It also recommends the UK Government considers changing the basis of the Barnett Formula to take account not only of population but also Scotland’s comparatively higher death rates and ageing population “given these factors lead to significant cost pressures for the Scottish Government”.

The report concludes: “There is a case for sub-national migration powers for Scotland to be further considered based on the evidence we have received…We call for closer co-operation between the UK and Scottish Governments on this issue.”

The SNP’s Pete Wishart, who chairs the committee, said it was encouraging Scotland’s population, now 5.37 million, was at its highest ever level, yet he noted its predicted growth still fell behind that of the UK as a whole.

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Stressing how population growth was necessary for the success of the Scottish economy, the Perth MP noted: “If we fail to keep pace with the rest of the UK there will be an economic cost to Scotland and an impact on our ability to support our social and economic ambitions.”