Nicola Sturgeon has said she will not seek a green light for another independence referendum in an emergency debate on Holyrood's response to the UK's Brexit vote - but is asking for a mandate "to explore the options that exist".

Scotland's First Minister will call on MSPs to support her talks "for protecting Scotland's relationship with the EU and Scotland's place in the single market".

The SNP leader said it is "one of the most important debates that parliament has had possibly in the history of devolution" - and stressed she will "explore all options" to keep Scotland in the European Union (EU) up to and including independence.

Ms Sturgeon met President of Ireland Michael D Higgins in Glasgow to discuss ties between their two countries.

Speaking after the meeting, she told the Press Association: "It may be that independence is the only way that we can protect Scotland's position in the EU but I have said that I am not starting from that assumption.

"I am starting from the determination to protect Scotland's interests and looking at all of the options.

"I am not asking parliament tomorrow to give us a green light for an independence referendum - I'm asking for a mandate to explore the options that exist."

Two former Labour shadow Scottish secretaries have backed efforts to keep Scotland inside the EU.

Ian Murray, who resigned from Jeremy Corbyn's shadow cabinet at the weekend, said "nothing is off the table" in Scottish Labour's bid to protect Scotland's EU membership - including support for another independence referendum.

Margaret Curran, who held Labour's Scottish portfolio while the party was leading the Better Together campaign, said "the case for independence in 2018 could be stronger than in 2014" after the Brexit vote.

Ms Sturgeon added: "As we go through this process it may very well be that the only way to protect our position in Europe is to consider independence.

"If we get to that stage that will be a specific decision for parliament to take, and at that stage I would hope to persuade the Labour Party and many others that is the right thing for Scotland."

Labour, the Liberal Democrats and Greens have all signalled their support for the EU motion.

Scottish Labour leader Kezia Dugdale said: "Every possible avenue must be explored to not just mitigate the impact of Brexit, but to strengthen our ties with our European neighbours."

Scottish Liberal Democrat leader Willie Rennie said: "I committed my party to supporting Nicola Sturgeon's special EU negotiation process as there is a strong need for cross-party support."

It is understood the Scottish Conservatives will seek to amend the motion.

Leader Ruth Davidson said: "It is encouraging that the First Minister has already held discussions with the UK Government and London Mayor to further this approach.

"However, we would caution the SNP against using these negotiations to further their aim of independence."

A series of polls since the Brexit vote on June 23 have suggested Scotland now favours independence.

A Survation poll of 1,002 adults for the Daily Record immediately after the Brexit vote found 53.7% saying they would vote for independence, against 46.3% in favour of staying in the UK.

Ms Sturgeon has accused Boris Johnson of launching "Project Farce" by leading the UK out of the EU.

Mr Johnson, who spearheaded the Leave campaign and is widely tipped to replace David Cameron as prime minister, declared "Project Fear is over" after Chancellor George Osborne said his proposed emergency Brexit budget is now unlikely to happen until the autumn.

In response, Scotland's First Minister wrote on Twitter: "Indeed, Boris. Project Farce has now begun - and you are largely responsible."

Scottish Secretary David Mundell accused Ms Sturgeon of "opportunism" to further the "independence agenda".

He insisted the arguments for Scotland being part of the UK are "as compelling today as they were in 2014".

But he sidestepped the question of whether Westminster would grant the powers for a second independence referendum to be held.

Mr Mundell told BBC Radio Scotland: "Could there be another referendum? Of course there could, that's a process issue.

"Should there be another referendum? That's a quite different issue, and my view is that there should not be another independence referendum."

Prime Minister David Cameron's official spokeswoman said: "What we all need to do is focus on getting the best deal for Scotland and the UK in these negotiations and the last thing that Scotland needs now is a divisive referendum."