NICOLA Sturgeon told Theresa May she wasn’t bluffing over holding a Scottish independence referendum.

The First Minister made the warning after at a “frustrating” meeting of the Joint Ministerial Committee in Downing Street,

Sturgeon also dismissed claims she was undermining the UK’s negotiating position.

‘I’m not seeking to undermine anyone. I don’t know what the UK’s negotiating position is, so there’s nothing there that I can see to undermine,’ she told reporters after the meeting.

Sturgeon, and the First Minister of Wales, Carwyn Jones, and Northern Ireland’s First Minister Arlene Foster and Deputy First Minister Martin McGuinness were all at the meeting yesterday. It was the first time the group has met since 2014.

“It was frank, it was at times robust, there was a fair amount of frustration in the room,” Sturgeon said.

She added: “We discussed the UK’s negotiating position in general, but it is safe to say we got no more information or detail on that than we had before we went into the meeting, and I got the strong sense the UK Government itself doesn’t know what it is trying to achieve.

“That is why many parts of the meeting were deeply frustrating, because we felt as if we weren’t getting any greater insight into the thinking of the UK Government.”

Sturgeon did say there was some movement on Scotland’s involvement in the Brexit negotiations.

She added: “We have still got a lot of work to do, and I think it is incumbent on the UK Government to inform that work by being much more open about what they are trying to achieve.

“I am determined, for my part, to do everything I can to work within this process as far as I can to protect Scotland’s interests.

“My frustration is that I am hearing warm words from the UK Government, but not backed up by substance or action.”

Downing Street has proposed a regular committee, chaired by Brexit Secretary David Davis, bringing together representatives from Scotland, Wales and Northern Ireland, with plans to meet monthly before the Prime Minister triggers Article 50, the process needed to start the the two-year Brexit process.

Sturgeon said she was pleased at the establishment of this group but warned a work programme was needed for that committee to have any meaningful Brexit influence.

“Wales voted to leave, but the people of Wales didn’t vote to be done over,” Jones told Sky News television after the meeting. “Access to the single market is the most important issue.” He also said he couldn’t see how it would be possible for Scotland to have a separate position.

Northern Ireland’s deputy first minister Martin McGuinness told reporters that “we believe we need to be at the heart of those negotiations”.

In Scotland, Scottish Tory Deputy leader Jackson Carlaw said the SNP were using Brexit as a “lever to crank up support for independence”.

“Last week, the SNP revealed its true colours by publishing a bill for a referendum that the majority of Scots do not want. It has them up shown up as a party utterly out of step with public opinion,” he said.

Scottish Labour leader Kezia Dugdale hit out at Sturgeon and May: “Reports that little to no progress was made at today’s meeting will be met with real frustration across Scotland.

“The results of the independence referendum in September, 2014 and the Brexit referendum in June, 2016 have provided the Scottish Government with a dual mandate: to keep Scotland in the UK with a productive relationship with the EU. Instead of advocating their own form of separatism with a hard Brexit or independence, both governments need to focus on the best deal for Scotland.”

A report published yesterday morning by the Institute for Government warned of a ‘full-blown constitutional crisis’ if the PM fails to secure an agreement on the Government’s approach with all nations of the UK.

The think tank said all four governments must agree the “core planks” of the UK’s negotiating position. Imposing a Brexit settlement on Scotland, Wales and Northern Ireland would be legal, but it would be a “reckless strategy” that would lead to the possible break-up of the UK.

Theresa May denies any suggestion of EU negotiations being a ‘binary choice’