They say Scotland could expect similar treatment to Ireland, which has had to accept London-formulated policy on migration as the price for relaxed borders.
Ronit Lentin, head of sociology at Trinity College, Dublin, said: “I’d expect there would have to be an ‘over-the-shoulder’ policy in Scotland as there is such a long, complex border between Scotland and England. You can’t monitor that unless you build a wall – but that’s not going to happen.”
Like Ireland, Scotland would not have border posts or passport controls between it and the rest of the UK, the experts say. But as the “smaller partner”, Scotland would have to accept UK migration demands.
The experts add that police in Northern Ireland board buses and trains to check on possible illegal immigrants.
The Irish position is seen as important because the land border between it and Northern Ireland offers an example of the border controls that would apply between Scotland and England. The two nations have agreed to form a Common Travel Area that covers the British Isles, which allows mostly free movement of people.
The SNP has said the same rules would apply for an independent Scotland. But it also says it would want to encourage immigration for young people or families with children to help boost the population.
That runs counter to pressure in England. With the UK population expected to reach 70 million by 2027 – two-thirds of the rise due to migration – UK ministers say they want to cut levels “to the order of tens of thousands”.
Lentin added: “Scotland may well have to go for a stricter immigration policy in consultation with England. If Scotland was to provide a more lenient policy it would be seen as a back door to England.”
She said although there is free movement between Ireland and Northern Ireland, there have been reports of checks to prevent illegal immigrants finding an easy passage into Northern Ireland and on to the UK mainland.
“There have been some checks, which can be racist. People who are black are often asked to show their papers.”
Piaras Mac Einri, director of the Irish Centre for Migration Studies at Cork University, believes that Scotland would face pressure from England to comply with its requests.
He said: “They would seek to have a disproportionate degree of influence. It goes without saying that the English/London authorities would wish for the least possible change, for a variety of obvious reasons.”
A spokesman for the SNP insisted Scotland would have the freedom to set its priorities.
“An independent Scotland will have responsibility for its own migration policy. Scotland faces different issues from the other parts of the United Kingdom, and migration policy could be tailored to address the economic challenges of demographic change,” he said.