The prospects for Scotland's economy after Brexit are at the heart of the battle between its pro-independence first minister and British Prime Minister Theresa May, who wants Britain to stay united as it leaves the EU. Nicola Sturgeon has warned that leaving the bloc's single market will cause tens of thousands of job losses in Scotland, while May has said she will aim for the "best possible deal" with Brussels, for Scotland too.

Going at it alone raises a host of doubts about Scotland's economy including what currency it would use and how it could reduce a budget deficit of nine percent of gross domestic product, worse than crisis-hit Greece. But the future of the North Sea oil sector, centered on the city of Aberdeen, where Sturgeon's Scottish National Party held its conference this weekend, is the key concern. World oil prices have declined in recent years and the offshore stocks are depleting. Deirdre Michie, head of Oil & Gas UK, the leading association for the North Sea industry, told reporters the sector was going through "quite a sustained downturn."

The oil industry employs around 330,000 people across the U.K., including around 38 percent based in Scotland, many of them in Aberdeen. Aberdeen's business community is wary about another constitutional confrontation just three years after the last independence referendum in which Scotland voted to remain a part of Britain by 55 percent. Sturgeon's announcement last week of her plans for a referendum generates "continued uncertainty and it's just a matter of fact that business doesn't like uncertainty," said James Bream, research and policy director at Aberdeen & Grampian Chamber of Commerce. But Bream said he was not surprised by the announcement since "the argument about independence has never gone away" despite the result of the 2014 plebiscite. The unionist campaign in that vote was heavily focused on the economic benefits of being a part of the United Kingdom.