Europe Minister David Liddington became embroiled in a war of words yesterday over whether an independent Scotland would need passport controls at the English Border.

He claimed during a visit to Holyrood that Scotland may not have the UK's opt-out from the Schengen Agreement on free movement within Europe, and may not get EU membership at all. "The fact that the UK has an opt-out from Schengen means we are able to maintain the border controls that you don't have on the borders between Schengen countries," he said.

He claimed Scotland's membership of Europe was "not something that can simply be assumed," adding that membership requires "the unanimous agreement of every other member state".

But a spokesman for First Minister Alex Salmond said: "All of these tired old scare stories are demonstrably untrue. They are insulting to Scotland, and the only effect they are having is to boost support for independence.

"Scotland is part of the territory of the European Union and the people of Scotland are citizens of the EU – there is no provision for either of these circumstances to change."