The EU citizenship of the Scottish people may be up for negotiation if the nation becomes independent, the EU's top policymaker has suggested.
European Commission President Jose Manuel Barroso has apparently suggested that the EU citizenship of people in a region that secedes from a member state would have to be "negotiated within the international legal order".
Unionist parties say the comments expose the Scottish Government's claim that Scotland would automatically be accepted into the EU as "total nonsense".
The Scottish Government maintain that there is nothing in Barosso's response that suggests that Scotland will not retain its place in the EU.
Meanwhile, two veteran nationalists have told the Press Association that Scotland's ongoing membership of the EU cannot be taken for granted.
Independent MSP Margo MacDonald and her husband Jim Sillars, both former SNP deputy leaders, believe further negotiation will be required.
And Sillars, who remains an SNP member, believes other EU member states could block Scotland's entry into the EU, particularly if party rebels succeed in their bid to pull Scotland out of Nato.
The rare pronouncement from Barosso on the wider EU secessionist debate came in response to a question by Italian federalist politician Mara Bizzotto.
She asked if regional citizens would immediately lose their status as EU citizens, and the resultant rights and obligations, if the region secedes from the member state.
Barosso responded: "In the hypothetical event of a secession of a part of an EU Member State, the solution would have to be found and negotiated within the international legal order."
Labour MEP Catherine Stihler said: "Scotland will not automatically assume the many rights of the UK.
"There will have to be long, detailed negotiations with a great many bodies and institutions. The outcome of which can never be taken for granted."
A spokesman for First Minister Alex Salmond said: "An independent Scotland will remain an integral part of the EU, and nothing in this answer suggests otherwise, despite the desperation of the anti-independence parties to say so.
"As many experts have confirmed, 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 upon independence."
The SNP is preparing to vote on overturning its historic opposition to Nato - a move widely interpreted as an attempt to boost Scotland's international credentials.
However, the party leadership is facing a backlash from several MSPs and grassroots members, who have vowed to vote against the resolution at conference next month.
Sillars said: "A number of people in the SNP do not realise that the decision on independence, and the consequences thereof, profoundly affect other people in their foreign policy.
"The Baltic states joined Nato as protection against Russia, and there are problems inside the Baltic states with Russia and vice-versa.
"They are also members of the EU. They will be very concerned if there is any diminution of Nato's geographic integrity.
"It is naive for anyone within the SNP to believe we can just kick that aside as of no consequence without someone in Europe taking adverse action against us.
"The potential adverse action against us could be that in the middle of the referendum campaign, while the SNP is saying we will automatically be in the EU, one of the EU states could say 'that's not true and we will block it'.
"Anybody who says the legalities will tie the EU up is very naive. This is big stuff we're talking about. This is the withdrawal of the aircraft carrier from Nato."
MacDonald added: "We have still got a bit of negotiation that we would need to do on our own behalf, but certainly at this stage from the finish line I don't think anybody can make definitive statements about what all the parties would do."