Fresh concerns have been raised over Scotland's future in the EU if a Yes prevails when Scots go the polls to decide whether to secede from the UK.
The European parliament could block Scotland's membership of the EU if the country votes Yes.
MEPs have told EurActiv that even if Scotland manages to get the unanimous backing of all the member states its accession would still face a vote in the European parliament.
This was backed up by sources within the European People's Party, who said if Scotland did not pledge to move towards joining the euro it was a distinct possibility Scotland would be blocked from joining the EU.
Furthermore, unanimous backing is far from guaranteed, with countries such as Spain concerned about the impact events in Scotland could have on their own territorial integrity.
The source, from the Socialists and Democrats, said: “We are deeply concerned about the prospects of a yes vote in the referendum.”
"The opt-outs they're pushing for would make it very difficult for them to get membership", the source added. Scotland is seeking opt-outs from the euro, the Schengen area, and the British VAT rebate.
The concerns echo those of the President of the European Commission Jose Manuel Barroso. He recently told the BBC "it would be extremely difficult if not impossible" for an independent Scotland to secure EU membership.
The European Commission repeatedly has refused to comment on how the referendum would affect Scotland's EU membership. Scotland's vote could have much wider ramifications than its own EU membership.
Societe Generale analyst Albert Edwards has argued a Yes vote could be “as unpredictable and as uncontrollable as those of the late 1980s in Eastern Europe, which led to the ultimate demise of the USSR. The EU has been likened to a shark: if it stops moving, let alone goes backwards, it will die".