AN SNP minister has accused the UK Government of lying, as relations between London and Edinburgh continue to deteriorate and calls mount for a second independence referendum.

Referring to UK ministers, Scotland’s Brexit minister Michael Russell said it had become “very difficult to negotiate with people who aren't telling you the truth".

Mr Russell also said the SNP government had already decided the turf on which a second referendum would be fought, if the First Minister decided to called one.

Read more: Battle lines drawn over Brexit as Nicola Sturgeon says Scotland ignored

“That campaign will be very focused on the type of country we want to live in,” he said, describing a choice between an inward-looking, intolerant post-Brexit Britain and an outward-looking, welcoming independent Scotland.

The Scottish Conservatives said Mr Russell was embarrassing himself and his party.

Mr Russell’s comments follow the First Minister saying the prospect of a second referendum was “becoming ever clearer” after the UK Supreme Court ruled MPs should have a vote on the Article 50 trigger for Brexit, but Holyrood had no legal right to a say.

The court confirmed the Sewel Convention, under which Westminster does “not normally” encroach on devolved issues, was a purely political matter, and carried no legal weight.

Speaking on BBC Radio Scotland, Mr Russell said negotiations with the UK Government over Scotland's future were "getting harder by the day", and previous assertions that the UK and Scotland were equal partners in the union had been “blown out of the water”.

Read more: Battle lines drawn over Brexit as Nicola Sturgeon says Scotland ignored

He said the position had “got a little worse” since Tuesday’s court ruling “because the UK Government has asserted constantly that they put the Sewel Convention into legislation [the Scotland Act 2016], and that this was a guarantee of consultation.

“Now we consider, to be blunt with you, they weren't telling the truth. And it is very difficult to negotiate with people who aren't telling you the truth."

He said the Scottish Government’s proposal to keep Scotland in the EU single market - with Downing Street’s help - remained on the table, and the UK could still consider it.

However he added: “It is alas that Government that's closing down those options."

He also said any future independence referendum would be fought on the issue of what kind of country voters wanted Scotland to be - and whether it was like post-Brexit Britain.

He said: “The Tories are declaring the type of country they want this to be.

“It is an insular country. It’s country that is nervous of change and difference. It’s country that doesn’t welcome migrants. That is not the kind of Scotland we actually need.

“The Scottish economy needs to have a dynamic Labour market that attracts people from the EU, otherwise we are going to be in deep economic trouble.”

Asked why support for independence was not significantly different from the 45 per cent seen in the 2014 referendum, he said: “I think we have still got have a campaign of course, if that’s where eventually we end up.

“And that campaign will be very focused on the type of country we want to live in.

Read more: Battle lines drawn over Brexit as Nicola Sturgeon says Scotland ignored

“I think what the First Minister was saying and illustrating very very clearly indeed was that’s the question of what’s now arising.

“Do we really want to live in a country in which we are simply told what to do, there is no partnership of equals, there is no meaningful consultation, vital decisions are announced without even a nod to us? Do we want to live in a narrow, inward-looking country? Or do we want to be better than that? And that is the issue that is coming into sharp focus.”

Scottish Conservative deputy leader Jackson Carlaw said: “We need the Scottish Government to be engaging positively to help secure the best possible settlement for Scotland and the UK.

“Instead, we have a minister who would rather hurl insults from the sidelines.

“Mike Russell is lumbering from one unevidenced accusation to the next, and is only causing embarrassment to himself and his party in the process.”

Scottish Secretary David Mundell will meet Mr Russell and Finance Secretary Derek Mackay at Holyrood on Thursday to discuss the repatriation of powers from the EU after Brexit.

Read more: Battle lines drawn over Brexit as Nicola Sturgeon says Scotland ignored

A UK Government spokeswoman said: "The devolution settlement is clear that foreign affairs are reserved to the UK Parliament. The well-established Sewel Convention applies only to devolved matters.

"The 59 MPs who represent Scotland in the UK Parliament will scrutinise, debate and vote on the Article 50 Bill, alongside representatives from across the United Kingdom.

"We are consulting extensively with the Scottish Government and, crucially, engaging with people and businesses across Scotland.

"We are committed to working closely with the Scottish Government as we prepare to leave the EU, as we have done since the vote in June."