Former SNP deputy leader Jim Sillars has said the party's leadership live in a "parallel universe" over their support for the European Union.

In a speech in Orkney, Sillars said that SNP's support for independence and membership of the EU is a "glaring contradiction". He believes that the SNP's leadership must inhabit a "parallel universe" if they believe that EU membership benefits Scotland.

Sillars said: "There is a glaring contradiction at the heart of official SNP policy on Europe.

"If being in a United Kingdom of 60 million people, where we have direct representation, does not give Scotland the sovereignty it needs, in what parallel universe does the SNP leadership see Scotland's interests being advanced in a 28-member state union of 500 million people?

In the 1980s Sillars devised the SNP's independence-in-Europe policy. He now believes that after the organisation's expansion and loss of the national veto it does not protect small nations' are "crushed" in the EU.

He said: "Small countries are now easily crushed, their views swept aside, as was the case when Greece voted 61% against austerity but had it imposed anyway.

"In reality, Ireland, Portugal and Greece have had massive wage deflation and brutal austerity imposed upon them by the larger states like Germany and France.

"If independence from the British union was to our advantage in 2014, then independence from the European Union is certainly to our advantage in 2016.

"The contradiction of the SNP urging a vote for freedom in 2014 and a vote for restriction and limitation in 2016 cannot stand."

The SNP responded to Sillars' comments by saying that an independent Scotland in the EU would have a "seat and a voice" at Europe's top table.

An SNP spokesman said: "Being part of Europe is good for Scotland, in terms of jobs, prosperity and security.

"An independent Scotland would have a seat and a voice at the EU's top table - something we are currently denied.

"Independence and interdependence go hand in hand in the 21st century, as proven by the fact that many of the EU's member states are smaller than Scotland and many have only become independent in recent decades."

The official campaign for Scotland to vote to Remain in the European Union, Scotland Stronger In Europe, said that EU membership is in the country's best interests.

A Stronger In spokesperson said: "We are campaigning for a Remain vote on 23 June because the facts show that saying in Europe is in our best interests. For example, EU law protects crucial rights at work, including entitlements to paid holiday of at least four weeks a year, maximum working hours, anti-discrimination laws, and statutory paid maternity and paternity leave. In this referendum, the alternative to European protection for Scots is giving such powers to the government at Westminster.

"The arguments for remaining the EU stand on their own merits, but in terms of the independence referendum both sides stressed the importance of protecting our place in Europe. Therefore, the Stronger In campaign is a place where people in Scotland can together across other political divides, and potentially have a decisive impact on the UK-wide result."

Sillars started his political career as a Labour MP in 1970 until forming a breakaway pro-devolution Scottish Labour Party in 1976. He then went on to join the SNP in 1980 where he went on become an MP again from 1988 to 1992.