BREXIT could trigger a “significant constitutional debate” and lead to increased powers for Scotland, according to a leading academic.

Professor Drew Scott said a UK vote to leave Europe would reopen the devolution settlement reached before the Scottish Parliament opened in 1999. That was based on Scotland having EU membership, and meant that some matters were reserved to Westminster with the remainder being handled by Holyrood.

As long as the UK remained in the European Union, many devolved powers such as environment, agriculture and fisheries, and social policy were guided by EU law.

However, Scott – professor of European Union Studies at Edinburgh University – said powers over these matters would default back to Holyrood.

He told The National: “The 1998 devolution legislation enumerates the powers that are reserved, but not the powers that are devolved. So you’ll find under the powers that are devolved things like agriculture and fishing, forestry, economic development, transport and so on. A lot of the devolved powers are also regulated by laws made at European level, over agriculture for instance, so although it is devolved the law about farming is actually set in Brussels. The Scottish Parliament does not have that much say over the actual policy, although it has quite a bit of discretion over how it implements it.”

If the UK left the EU, Scott said there would be no agriculture policy driven by Brussels, which would raise the question of who controlled that policy in Scotland.

“Because it’s not on the list of reserved powers, agriculture policy automatically become a policy competence of the Scottish Parliament, which it is just now,” he added. “But the scope of that policy increases enormously. It’s not just about implementing CAP, it’s about actually designing a whole new agricultural policy for Scotland.”

Scott said there would then be questions about who would be responsible for funding the policy, which is worth more than £3.7 billion in Scotland.

“Although the policy defaults to the Scottish Parliament, it doesn’t have the money to pay for it because it has previously been paid for from Brussels money, which although we have paid for we haven’t actually seen,” he said.

Another example would be fisheries, he added, which was one of the most “iconic” European policies because “everyone believes Scotland was sold down the river when we joined in 1973”.

He said: “The question arises: who would control the catch that’s allowed in Scottish territorial waters? Does that come back to Scotland or does the UK Government call it ‘international policy’ and say that’s reserved?

“This isn’t about the SNP, the Labour Party, or the politics of Scotland – this is a situation that will emerge because of the way the Scotland Act was written in 1998 – it’s unavoidable if there’s Brexit.

“Technically, what I’m saying is where EU law exists the Scottish Parliament can’t legislate. EU law exists over agricultural policy so the Scottish Parliament can’t make law over that. But when EU law doesn’t exist, it’s up to the Scottish Parliament to make the law.”

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