Daniel and Jenny Whiteley are just the sort of young couple Scotland needs.

Mr Whiteley has a degree in astrophysics from the University of St Andrews and his wife is a management graduate.

Since graduating this summer they have been travelling, but when they return to the UK in January Mr Whitely is likely to be denied entry because he is a US citizen and his student visa has expired. Despite being married to a Scot and intending to settle in Scotland, new immigration rules mean he cannot live in the UK unless the couple have an income of at least £18,600 a year.

In October another US citizen, Dr Andrew Wilbur, and his Scots wife were forced to leave the country because they, too, failed to meet the threshold in the 12 months before application. At the time Mr Wilbur was studying for a PhD in human geography at Glasgow University and his wife's employment was interrupted by family illness.

The cap on non-EU migrants settling in the UK was brought in by the Coalition at Westminster, led by Conservatives who were elected on a pledge to crack down on immigration. Some control was required. In the south and east of England, communities where there has been a rapid influx of migrants have struggled to meet the new demands on services and infrastructure.

The income test is designed to reduce immigration from outwith the EU and ensure those who arrive in the UK also benefit the economy. Both Mr Whiteley and Dr Wilbur have already made a financial contribution through university fees and accommodation and living costs. Mr Whitely paid £70,000 for his tuition, spent £16,000 on accommodation and also contributed £5000 in tax and National Insurance.

The new rules on spouses were designed to deter marriages of convenience which are in no-one's interest; unfortunately for couples such as the Whiteleys and the Wilburs, they have been caught by a policy which makes no allowance for young people starting out on their careers.

This is not in the interests of a country like Scotland that needs talented migrants to settle here. Last week the latest census figures showed that although the Scottish population is at a record level, it is rapidly ageing, and the increase in the birth rate in the last few years is due to new migrants.

That was the rationale behind the Fresh Talent initiative, introduced by the previous Labour-LibDem administration in Scotland to persuade students to stay on after graduation and use their talents in this country. As The Herald has argued consistently, a one-size-fits-all immigration policy does not work when the conditions in Scotland are very different from those in the south of England. The cases of the Wilburs and the Whiteleys are examples of a policy that is not only unfair but sends out entirely the wrong message to the rest of the world.