An independent Scotland would have “zero technical problems” rejoining the EU immediately after Brexit, according to the World Trade Organisation’s former director Pascal Lamy.

He also predicted that a trade deal between the UK and the EU would take “five or six years” to negotiate, and an immediate transition deal would be needed.

Speaking at the Institute for Government, Lamy said: “Assume Scotland becomes independent and wants to join…

“If we have something of an overlap - zero technical problems.

“Maybe the number of votes which Scotland has in the European Council, the number of Scottish members of Parliament would have to be debated. Not a problem.”

The biggest obstacle would be the objection of Spain, which does not want to encourage Catalan secessionists, he predicted.

As Lamy spoke in Pall Mall, London, ten minutes' walk down the road, the Prime Minister Theresa May ruled out a second Scottish independence referendum before Brexit. On Monday, the First Minister Nicola Sturgeon had demanded one in Autumn 2018 or Spring 2019.

Lamy also shot down the idea previously advocated by the SNP that Scotland could negotiate a separate version of Brexit while staying in the UK.

“If there had to be something complex for the UK, and even more complex in Scotland, that would add complexity to complexity,” he said. “A simple solutions that comes to mind if Scotland wants to remain in the EU - vote for succession on their own terms and then they re-enter.”

Lamy, who headed up the WTO between 2005 and 2013, also said he did not like Foreign Secretary Boris Johnson, who he knew from when the Johnson family lived nearby him in Brussels.

“I saw Boris as a nasty young kid,” he said. “He never changed.

“We credit the British with a very specific eccentricity. Imagine someone from Sweden or Norway acting like Boris.”