European Union leaders are down-playing an independent Scotland's right to EU membership to compel it to join the euro, open its borders and pay more towards the European budget, according to a senior German government adviser.

Professor Dr Roland Vaubel, an adviser to Germany's economics ministry, said EU treaties were "consistent with automatic succession of both the seceding state and the rump state".

But he added that international leaders "have a vested interest in centralisation" and "are biased against secession".

A string of European leaders, including EU Commissioner Jose Manuel Barroso have all suggested that Scotland would need to re-apply as a new state if it left the UK.

Dr Vaubel said their position was based on a desire "to renegotiate the terms of Scottish membership", to bring them into the euro and give up the budget rebate negotiated by Margaret Thatcher in 1980s.

But he said the European leaders' arguments had "no basis in the European treaties".

He added: "The opinion of the European Union institutions that Catalonia and Scotland, after seceding, would have to re-apply for EU membership has no basis in the European treaties. Nor has this question been settled in any UN agreement.

"By putting politicians and bureaucrats of different countries under competitive pressure, secession improves performance."