COUNTRIES already in the EU could add a long delay to an independent Scotland's plans to join the union, a top academic has warned.

European law expert Professor Kenneth Armstrong of Cambridge University said political manoeuvring by current member states could double the 18-month timetable for joining the EU expected by the SNP.

He told Holyrood's European committee: "We should not be surprised if another member state - and it could be Spain - should exercise or threaten to exercise the veto."

The Spanish government is keen to discourage the independence movement in Catalonia and the Spanish Prime Minister, Mariano Rajoy, has already dismissed the SNP's claim that an independent Scotland's membership would be fast-tracked.

Mr Armstrong reminded the committee that in the 1960s the UK was kept out of the EEC by France for political reasons.

"De Gaulle said non," he said.

Political manoeuvring could add between six months and 18 months to the SNP's proposed timetable, he said.

He also warned that the SNP's proposal for fast-tracking an independent Scotland into the EU, using Article 48 of the Lisbon treaty rather than the usual accession process set out in Article 49, was "legally implausible and incredibly politically risky".

He warned: "We know that very strong elements within the Conservative Party would want to reopen treaty negotiations on a whole host of other things, which would then bog down the entire negotiation process and may ultimately lead to its failure."

Sir David Edward, a former European Court judge who also gave evidence to the committee, said the treaties were unclear on what should happen over membership in the event of Scottish independence.

He said: "So as far as the treaties go there is no solution to this problem, but I go back to what was said to me by a very experienced Dutch foreign servant, and later the Dutch foreign minister, on the problem of the euro.

"He said: 'We will find a way, we always do.'"