Nicola Sturgeon has set out fundamental questions the Prime Minister must answer about Brexit, demanding Theresa May make clear the "general direction" the UK will take in the wake of the vote to leave the European Union (EU).

The Scottish First Minister, who has repeatedly warned another vote on independence from the rest of the UK is likely, said it would be impossible to navigate the "choppy waters" brought about by the referendum.

The SNP leader defended her stance of keeping a second independence vote on the table, saying: "If we don't retain the option we would be accepting that no matter how damaging to our economy and society Westminster decisions turn out to be, we would be powerless to choose a better future.

"I don't think that would be sensible or an acceptable position to place ourselves in."

The First Minister addressed a lunch held by the Journalists' Charity in Glasgow, telling the audience it is "highly unlikely" the UK will stay in the single market.

Ms Sturgeon has already made clear that she regards remaining in the free trade zone as being vital for the UK.

As SNP ministers consider the prospect of a second independence referendum, the First Minister stressed they would judge the options available "against this fundamental question - does it protect our key national interest?"

She criticised the UK Government over the "continued lack of clarity about what exactly is going to happen next".

Ms Sturgeon, speaking three months after the European vote took place, said the "twists and turns" that had occurred since then "could scarcely have been conceived by any scriptwriter for any soap opera".

She added: "Recent events might have felt like a soap opera but the one script line that should have been written months ago still hasn't even been drafted - and that matters and it's going to matter more with every day that passes.

"That script line, of course, is what does Brexit actually mean? What does it mean for our economy, for jobs, trade and investment, what does it mean for our universities, our scientists, our farmers?

"What does it mean for travel across this continent for those who choose to live in an EU country other than their own?

"It is quite extraordinary to think this three months on, but right now there are no answers to any of these questions, or the plethora of other questions people are understandably asking."

The SNP leader said: "Today is the three-month mark from the referendum, there are a multitude of questions that remain unanswered.

"I want to set out three of the most important I think must be answered, and must be answered soon, because they are fundamental to our economy and our people.

"First, does the Prime Minister want us to remain in the single market? I accept that achieving that will take negotiation but surely we must know whether or not that is an objective.

"Second, will we need visas in the future to travel to Europe? Is the UK setting us on a path where we will see a holiday tax imposed upon us?

"Thirdly, will workers' rights be guaranteed, holiday pay, maternity rights, the things that we all have come to take for granted, are they guaranteed or are they all at risk?

"On these vital practical questions there have been no answers. I accept that at this stage the Prime Minister can't answer every question, but I do think it is reasonable to expect that the general direction of travel is set out.

"Because none of us, whether in government, across business, across society, can properly plan for the next few years without some of that general direction being made clear.

"These are really serious and important decisions, we have a difficult road ahead to navigate our way through, we must start seeing the detail of where things are going."