CLAIMS that Holyrood would gain sweeping new powers if Britain quits the EU have been blasted as a "Tory con trick" by John Swinney.

The Leave campaign has consistently attempted by sell Brexit to Scottish voters who back further devolution or independence by arguing it would see influence over policy areas such as farming and fishing transferred from Brussels to Edinburgh.

The claim has been backed up by some academics, including Professor Drew Scott, professor of European Union Studies at the University of Edinburgh and a former advisor to the SNP Government on Europe, who has said Holyrood would gain new powers "by default" under the existing arrangement that sees anything not explicitly reserved to Westminster devolved.

Read more: How Brexit could open up new constituency of support for independence among middle-class Scots

Campaign group Leave.EU yesterday said that Holyrood can expect to win control of £709m worth of farming subsidy and grant payments if the UK rejects the status quo next week, with the parliament seeing its budget boosted by another £500m a year as a result of cash the UK would save out of the EU.

However, with a new poll showing the race in Scotland tightening, the Deputy First Minister angrily rejected the argument. Mr Swinney warned that quitting the EU would see the "extreme right-wing" of the Conservative Party at Westminster, rather than Holyrood, wield additional control over Scotland.

He said: "Leaving the EU does not mean extra powers would be transferred to the Scottish Parliament – the powers would go straight back from Brussels to Westminster, who would have absolutely no obligation to devolve anything.

The Herald:

"The only people who would be empowered by a Leave vote would be the extreme wing of the Tory party – people who most certainly do not have Scotland’s best interests at heart, and people who are determined to rip up the various workers’ rights and employment protections guaranteed by the EU.

"Indeed, the Leave campaign is led by the very same people who have, at every opportunity, resisted the transfer of powers to Scotland – so their hollow offers of more powers are nothing more than a Tory con-trick.

"The way to get more powers for the Scottish Parliament is for Scotland to become an independent nation – not to cross our fingers for a Damascene conversation from Boris Johnson and Michael Gove."

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Mr Swinney spoke out as a new Ipsos Mori poll showed the race in Scotland is tightening, although Remain still enjoys a substantial lead a week before the crucial vote.

The survey put support for Remain in Scotland at 58 per cent, while a third support Brexit and 8 per cent are undecided. With undecided voters removed, 64 per back Remain and 36 per cent Leave. It showed support for Remain in Scotland has fallen 13 points in the last six weeks.

UK-wide polls in recent days have consistently shown the Leave campaign opening up a lead over Remain.

The Herald:

Mr Swinney added: "The polls in this referendum are extremely tight – and Scotland can play a decisive role in the outcome. By voting Remain next Thursday, the people of Scotland can reject this right-wing Tory takeover and vote to protect the substantial social and economic benefits we enjoy as part of the largest trading block in the world."

Speaking in February, Prof Scott said control over areas such as fishing and farming that are currently wielded by Brussels would automatically default back to Holyrood. He said this would create a "significant constitutional debate" about how these new powers should be exercised and paid for. The current devolution arrangement means that while some matters are declared as being reserved to Westminster, everything else is controlled by the Scottish Parliament.

Read more: Nicola Sturgeon - EU vote is not about Scottish independence

This week, justice secretary Mr Gove went further, claiming Scotland could have a say over immigration policies if Britain leaves the EU, even though policies would continue to be controlled by the Home Office. Mr Gove's intervention over immigration was swiftly refuted by senior SNP figures, including Nicola Sturgeon, although long-standing arguments over fishing and farming have largely gone unchallenged.

Senior SNP sources insisted that negotiations over policies such as fishing quotas would have to be negotiated internationally even after Brexit, meaning it would fall under Westminster's remit and leave Holyrood with no say.