Media playback is unsupported on your device Media caption Scotland's First Minister, Nicola Sturgeon: A hard Brexit creates a "fundamental question for Scotland"

Nicola Sturgeon has warned Theresa May that she is not "bluffing" on the promise of a second independence referendum if Scotland is "driven off a hard Brexit cliff".

Scotland's first minister told the BBC's Andrew Marr she felt the prime minister had "no plan" in terms of her strategy for the UK leaving the EU.

She said she was prepared to compromise and wants Mrs May to do the same.

The UK government has said a special deal for Scotland is unrealistic.

The prime minister said on Sunday morning the government's thinking on Brexit "isn't muddled at all".

In an interview on Sky News, she said her priority was to get the "best possible deal in terms of our trading relationship with the European Union".

Brexit talks with the EU are expected to begin as early as April.

Scottish opposition parties have called for Ms Sturgeon to rule out a second independence referendum.

Voters in Scotland backed the UK staying in the EU by 62% to 38%.

Ms Sturgeon has said she wants the UK to retain membership of the European single market, the so-called soft Brexit option.

'Opportunity to decide'

She has also indicated a soft Brexit would see the prospect of Scottish independence "put aside" in the short term.

However, in an interview for the Andrew Marr programme, she warned the UK government and Mrs May that "they will be making a big mistake if they think I am in any way bluffing" on the prospect of another Scottish independence referendum.

She said that if the UK opts for leaving the single market then she would "give Scotland the opportunity to decide whether it wants to be driven off a hard Brexit cliff by right-wing Tory Brexiteers or whether it wants to take control of its own future".

Asked if she was looking at a referendum "much quicker" than in five or 10 years' time following a hard Brexit she said: "I would think, yes. But let me not get away from this point, I'm putting to Theresa May a compromise solution."

Image caption Theresa May and Nicola Sturgeon met for talks in Edinburgh after the UK voted to leave the EU

Ms Sturgeon also told the BBC presenter that discussions with the UK government over the Brexit options had left her "frustrated".

She said: "I don't feel as if I know any more about her (Theresa May's) negotiating objectives than I did six months ago."

Asked if she seriously thinks "there is no plan", the first minister said: "Yes I do".

She added: "I say that with a lot of regret as that puts every part of the UK into a very perilous position."

Analysis by BBC Scotland political correspondent Nick Eardley

Will another independence vote happen?

Nicola Sturgeon has warned she isn't bluffing over a second independence referendum. But she's also been careful to emphasise she is offering a 'compromise' that would take one off the table. For now all options remain in play.

A key influencing decision will be whether Scotland stays in the EU single market, either as part of the UK or in a separate arrangement. Prime Minister Theresa May said today she does not intend to keep bits of membership - instead she wants an ambitious trade deal with Europe. More details in the next couple of weeks.

But the first minister will also be reluctant to call one unless she's confident she'll win; at the moment polls suggest support for independence has not increased since 2014.

Ms Sturgeon has tried to put the ball in the prime minister's court; asking her will she listen to the views of the Scottish government? If not, Ms Sturgeon thinks Scotland will have to ask itself if it's happy with the decision. Watch this space.

Ms Sturgeon highlighted a meeting at Downing Street in October which also involved the first ministers of Wales and Northern Ireland.

She said: "I'm not exaggerating too much when I say the prime minister sat on the other side of the table at that meeting and said 'Brexit means Brexit' and not a lot more.

"I came out of that meeting more frustrated, after a meeting of that nature, than I have ever been before."

In the interview, the SNP leader also said she accepted "it looks at the moment as though the UK is going to leave the EU".

She called on Theresa May to work towards a "compromise" and "common ground that avoids the worst impacts".

'Damaging uncertainty'

The prime minister has pledged to trigger Article 50 of the Lisbon Treaty - getting leaving talks with the EU under way - by the end of March.

Talks can take up to two years, unless an agreement is reached to prolong the process.

Responding to Ms Sturgeon's comments, Scottish Conservative leader Ruth Davidson said: "This week we've seen Nicola Sturgeon say that she was going to take a referendum off the table, only for her and Alex Salmond to put it back on the table again today.

"The first minister needs to start acting in the interests of all Scots, not simply playing to her nationalist base."

Kezia Dugale, Scottish Labour leader, accused the SNP of sowing "division and uncertainty".

"With a growing crisis in our NHS and a shameful gap between the richest and the rest in our schools, the challenges facing Scotland are too great for the SNP government to be distracted by another referendum," she said.

Scottish Liberal Democrat leader Willie Rennie said Ms Sturgeon was causing "damaging uncertainty".

He added: "She rightly criticises the prime minister for a lack of clarity on Brexit but the first minister is making matters worse with a similar lack of clarity on independence."

The full interview with Nicola Sturgeon was broadcast on The Andrew Marr Show and will be available later on the BBC iPlayer.