Scottish Government plans to stay in the single market after exiting the European Union (EU) would "not be deliverable", the UK Brexit Secretary has said.

Responding to the Scotland's Place in Europe proposals, David Davis wrote there were "clear barriers" to plans for Scotland to join the European Free Trade Association (Efta) and then the European Economic Area (EEA).

Mr Davis, writing to his Brexit counterpart in Scotland Mike Russell, said the options outlined in the paper could create internal trade barriers in the UK, leading to "significant disruption".

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He said: "Scotland's accession to Efta, and then the EEA, would not be deliverable and, importantly, would require the consent of all Efta and EU member states.

"Any divergence between EU and UK law - as a result, perhaps, of new EU regulation - could lead to the creation of new barriers to trade within our Union, which could take the form of additional controls and checks on trade within the United Kingdom.

"Given that trade with the rest of the UK is worth four times trade with the EU, I do not believe that such significant disruption to the internal UK market is in Scotland's - or the UK's - best interests.

"Scotland's businesses could face a confusing mix of regulatory regimes."

He was "disappointed" the Scottish Government called for a second Scottish independence referendum before officials could complete work on responding to the white paper.

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Replying in writing, Mr Russell told Mr Davis: "It is important to restate the fundamental importance the Scottish Government places on membership of the European single market as distinct from the UK Government's ambition of having access - or partial access - to this market.

"Scotland's Place in Europe clearly sets out this distinction and the damage to Scotland's economy and society that will occur if Scotland's single-market membership is jeopardised.

"In relation to the specific points you raise regarding the proposals in Scotland's Place in Europe, there is every reason to suggest that with the necessary political will and commitment these issues could have been addressed.

"Indeed, there were no insurmountable issues raised in the engagement between officials that took place over the last two months."

Mr Russell wrote that he was disappointed his Brexit meetings with the UK Government had "not enabled proper discussion or engagement" and led to a negotiating position reached solely by the UK Government rather than a more collaborative approach.

He called for more meaningful meetings which provide "real opportunities" to influence the Brexit process.

Mr Davis's letter was sent on March 29, the day the Prime Minister triggered Article 50 and started the formal process of the UK leaving the EU but was not published by the Scottish Government until Friday.

Scottish Secretary David Mundell claimed the Scottish Government had asked for the response not to be released but Mr Russell denied this and said the UK Government had refused to publish it.

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Mr Russell's spokesman added: "The UK Government has been desperate not to publish its own letter, and no wonder - it simply exposes how little Theresa May's Tories have engaged with our proposals to keep Scotland in the single market.

"Their reckless pursuit of the hardest of hard Brexits directly threatens tens of thousands of Scottish jobs as well as posing a danger to investment and our wider economy."

Commenting on David Davis's ruling out of a differentiated relationship with the EU for Scotland, a Scottish Labour spokesman said: "The Tories' reckless pursuit of a hard Brexit will not only damage our economy - it has put the union at risk once again.

"At a time of such uncertainty, Scotland deserves better than two governments - the Tories and the SNP - which have adopted such extreme constitutional positions and are so determined to create deep divisions with our closest neighbours.

"A Labour government would rip up the Tories' Brexit white paper and make sure we keep the closest possible ties with our continental allies.

"Labour is the only party that stands for what the majority of people want - Scotland in the UK while keeping the closest possible ties with Europe."