NICOLA Sturgeon will have to wait until Scotland is half-way out of Europe before holding a second independence referendum, it has emerged.

A draft referendum bill and consultation, published yesterday, indicate that spring 2018 will be the first feasible date that a new vote could be held despite previous speculation that it could take place as early as next year.

Experts said the timetable raises significant doubts over whether Scotland would be able to remain a member of the EU when the UK quits in early 2019, even if voters have backed independence to protect the country's relationship with Europe.

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Ahead of the last referendum, the Scottish Government said it would take 18 months following a Yes vote to become an independent nation. A similar timescale would see Scotland faced with leaving the EU along with the UK, regardless of the second referendum result.

Kirsty Hughes, an EU expert and a member of the Centre on Constitutional Change, has previously said that a new referendum would have to be held and won early next year if Scotland is to remain in the EU, rather than having to go through a more complex process of leaving and re-entering at a later date.

She said that in light of the new timetable, the best Scotland could hope for would be a streamlined process for rejoining the EU, potentially enjoying Norway-style terms before being accepted as a full member within a few years.

Ms Hughes added: "If there was a vote for independence in early 2018 that gives the EU a bit of time to work out how not to disrupt Scotland’s place in the EU. I very much doubt Scotland could take on the UK’s membership, so the question becomes how to handle the transition. If Scotland is to become a new member state, accession treaties will take a couple of years.

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"With a year’s notice and political goodwill on all sides, they could create a straightforward process. There might be some sort of transitional relationship, such as remaining in the EEA. But I don't see any way Scotland becomes independent in early 2019 and is a full member state at that point."

SNP ministers have confirmed that they will have to seek the UK Government's permission to hold a new referendum, with the process largely following precedents leading to the historic 2014 vote, when 55 per cent rejected independence.

A consultation over the draft bill will last until January, and if the First Minister decides to push ahead with another referendum, a Section 30 order will have to be granted by the UK Government before the bill is introduced to Holyrood.

The process for granting a Section 30 Order, which would temporarily transfer powers to hold a legally-binding referendum to Holyrood, took four months over late 2012 and early 2013. A new Edinburgh Agreement between the two Governments, setting out the terms of the vote, may also have to be negotiated.

With finance secretary Derek Mackay confirming that it would take six to nine months for the bill to progress through parliament once introduced, it would be impossible for MSPs to pass it before parliament breaks up for summer recess in July.

While it may be ready after the parliament returns in September, after it passed it would then take another four weeks to receive Royal Assent, assuming it is not challenged in the courts. The Bill specifies that a 16-week 'referendum period' will be held before polling day, pushing the earliest possible referendum date well into 2018.

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There also remains the possibility that the UK Government could block the vote by refusing to grant a Section 30 order. Ms Sturgeon has said it would be "inconceivable" that Theresa May would refuse a request, but Number 10 yesterday said that the First Minister had "no mandate" for another referendum. Asked if UK ministers would reject a call for a second referendum from the Scottish Government, a spokesman stated: "There has not been a call."

The Scottish Government is under no obligation to introduce the Bill to parliament, however, Ms Sturgeon has indicated she will move for a second vote if a string of demands for additional powers for Holyrood, to be revealed within weeks, are not met.

She faced criticism from opposition MSPs after the independence bill proved the first major legislation published by the Scottish Government since the May election, despite previous pledges to make issues such as education and mental health priorities.

Ruth Davidson, the Scottish Tory leader, said: "Nicola Sturgeon stated quite clearly she would only hold another referendum if that’s what the people of Scotland want. But the voters were clear in 2014 that they didn’t want to break up Britain and poll after poll has shown that support for another divisive referendum is tumbling.

"No matter what else the SNP claims to be passionate about, be it education, health or justice, today’s publication exposes its sole objective is separation ahead of anything and everything else."