FIRST Minister Nicola Sturgeon is being “held back” from fully supporting a referendum on the final Brexit deal by her advisers, according to a senior source close to the Scottish Government.

The insider, speaking on condition of anonymity, said key members of Sturgeon’s top team were worried about the impact a new vote would have on another independence referendum.

Scottish Liberal Democrat leader Willie Rennie, who last week urged the SNP leader to back a “people’s vote” on Brexit, said: “Her special advisers seem to have a vice-like grip on the First Minister.

"It would be wise for Nicola Sturgeon to talk to others and to open her mind to the best way of keeping our country in the EU.”

Sturgeon has delayed revealing her intentions for a second independence referendum due to what she regards as a lack of detail on the UK’s future relationship with the EU.

The First Minister is expected to provide an update once a fuller picture emerges from the negotiations between Prime Minister Theresa May and EU representatives.

However, a number of senior SNP figures believe a second independence referendum will not occur before 2021 because May will refuse to sanction another vote. These figures want Sturgeon to instead throw her weight behind the cross-party campaign for a referendum on Brexit.

Senior nationalists believe backing this short-term move would put the SNP on the side of the majority of Scots, while also reaching out to Remainers who are hostile to independence.

Advocates of this approach also believe that, by shifting her constitutional position in this way, Sturgeon would give herself breathing room on independence and space to reboot the case for independence.

It is understood Cabinet Secretary Michael Russell, as well as SNP Westminster leader Ian Blackford, are open to another Brexit referendum, while Sturgeon herself is said to interested, but she has only offered qualified support.

A senior source close to the Government said the First Minister’s special advisers – the political appointees who work for ministers – are sceptical and Sturgeon is being “held back”.

The insider said two of her most influential “spads” – chief of staff Liz Lloyd and constitutional adviser Ewan Crawford – are not convinced by the policy.

Some doubters are said to be worried that backing another Brexit vote would create a precedent for a “double referendum” on independence: one on the principle, and another on a final deal.

However, SNP supporters of another Brexit vote point to a recent report by the Constitution Unit which they believe should allay these concerns.

The report recommended that, in cases where a Government produced a White Paper outlining a change to be offered in a referendum, a further plebiscite would only be triggered if there was a “material” departure from the original prospectus.

Asked by Rennie last week about a final vote on Brexit, Sturgeon said: “If Willie Rennie wants me to be an enthusiastic advocate of such a vote, let him explain to me how it would guarantee that we will not simply find ourselves in the same position we found ourselves in June 2016, when Scotland voted to remain in the EU but the rest of the United Kingdom voted to leave.

“If he can explain right now how Scotland is guaranteed that it will not find itself in that position, I am happy to talk to him further about the matter.”

She added: “If I am to get enthusiastically behind the campaign for another EU vote, surely it is not unreasonable to ask for a guarantee that Scotland would not find itself in that position all over again.

“The fact of the matter is that Willie Rennie and others campaigning for a people’s vote are unable to give that guarantee.

“If they are prepared to give such a guarantee, I am happy to get behind the campaign.”

Ian Murray, Labour MP for Edinburgh South, said: “I wrote to Nicola Sturgeon asking her to join the People’s Vote campaign, and it’s deeply disappointing that she has declined to do so.

“She needs to put the country before the narrow interests of her own party and her independence crusade.

“The People’s Vote campaign is a cross-party group including Labour, Tories, LibDems and Greens. If the First Minister truly is committed to fighting against a hard Brexit then she will join us; failure to do so will confirm that she is only interested in grievance – again, a political party putting its ideology before the country.”

A spokesperson for the First Minister said: “As the First Minister has repeatedly made clear, the SNP will not stand in the way of a second EU referendum – but those advocating it need to explain how they would guarantee that we will not simply find ourselves in the same position we found ourselves in June 2016, when Scotland voted to remain in the EU but the rest of the United Kingdom voted to leave.

“We are open to discussions with the campaign on any suggestions they may have to address that flaw in their current proposals."

The spokesperson added: “With it now looking increasingly likely that the choice facing the UK will be between a no-deal Brexit or a blind Brexit, an extension to the Article 50 negotiation period must be on the table as the only way to avoid an economic cliff edge – and allow all alternative options to be considered.”