NICOLA Sturgeon is to unveil a blueprint for a second independence referendum within days after warning Theresa May she is not bluffing about a pre-Brexit vote to break up the UK.

The First Minister announced a draft referendum bill would be published next week and indicated she was ready to go to the country before the UK formally withdraws from the EU in early 2019 unless Westminster delivers sweeping new powers for Holyrood.

Her announcement, on the opening day of the SNP conference in Glasgow, prompted bookmakers to slash the odds on a second referendum, and coincided with her predecessor Alex Salmond urging her to hold another vote even if there was no majority for Yes in the polls.

Read more: John Swinney says SNP could keep pound policy in new referendum

Academics predicted that chaos caused by the UK formally serving notice to quit the EU next spring could prove a potent "recruiting sergeant" for independence.

The SNP leader's remarks drew immediate criticism from the main opposition parties at Holyrood, with both the Tories and Labour accusing her of putting her dream of independence above issues such as health and education.

Ms Sturgeon called on Ms May to "prove" Scotland was an equal partner within the UK as she railed against hardliners in the Conservative Party who appear to be succeeding in their push for a 'hard' Brexit that would mean leaving the single market.

She said demands would be published within weeks for new powers for Holyrood which will include immigration and the ability to strike international deals. She also called for areas of policy currently under the remit of Brussels, such as fishing and farming, to be transferred to Edinburgh.

Issuing a direct message to Ms May, the First Minister said: "Hear this - if you think for one single second that I'm not serious about doing what it takes to protect Scotland's interests, then think again.

"If you can't - or won't - allow us to protect out interests within the UK, then Scotland will have the right to decide, afresh, if it wants to take a different path.

"I am determined that Scotland will have the ability to reconsider the question of independence - and to do so before the UK leaves the EU - if that is necessary to protect our country's interests. So I can confirm today that the Independence Referendum Bill will be published for consultation next week."

The announcement drew a rapturous standing ovation from delegates, who were warned that in the case of a second referendum they would have to "engage the arguments with a fresh eye and an open mind."

But Ms Sturgeon added: "If the choice we face is an inward looking, insular, Brexit Britain, governed by a right wing Tory party, obsessed with borders and blue passports at the expense of economic strength and stability.

"Or a progressive, outward looking, internationalist Scotland, able to chart our own course and build our own security and prosperity, then know this - that is a case we will win."

Read more: John Swinney says SNP could keep pound policy in new referendum

The comments came with the question of a second independence referendum set to dominate the three-day gathering.

The First Minister admitted she receives conflicting advice every day over the timing of a second vote but issued a thinly-veiled call for unity within the party, telling party members: "I know I can count on your support every step of the way."

Mr Salmond, in remarks that could be deemed unhelpful to Ms Sturgeon, ramped up pressure for a vote sooner rather than later as he dismissed concerns from independence supporters who want to see more favourable polls before committing to new referendum.

A poll for The Herald, published yesterday, indicated that even a 'hard Brexit' which the First Minister has campaigned against would leave the country divided down the middle over whether a second referendum should be held. A new BMG tracker poll for this newspaper found 47 per of Scots would vote to remain in the UK if there was a second referendum tomorrow, with 39 per cent saying they would back independence, and 12 per cent undecided.

Stripping out don't knows, support for a Yes vote was 45 per cent, with No on 55 per cent, the same result as the 2014 referendum.

But the former SNP leader said: "Will Nicola Sturgeon push the button on a referendum if support for independence is, say, 50:50 or at that level? Well, I hit the button for a referendum when support was 27 per cent. Why would she be reluctant on a much larger level than that?"

A consultation over the draft referendum bill will now be held, although Ms Sturgeon will be under no obligation to introduce it to Holyrood. It remains to be seen whether the UK Government would grant to power to hold a legally-binding vote, with power over the constitution reserved.

While the SNP does not hold a Holyrood majority, there are more pro-independence than pro-union MSPs in the Scottish Parliament taking into account the six Greens. The Green co-convenor Patrick Harvie has already said his party would back a second referendum if it comes to a vote.

Dr Chris Hanretty, a reader in politics at University of East Anglia, said a chaotic Brexit may prove "the best recruiting sergeant the SNP could imagine." He added: "Scots voted against independence because it involved more risk than continued membership of the United Kingdom. Now that we are leaving the EU, union no longer seems like such a safe bet."

Read more: John Swinney says SNP could keep pound policy in new referendum

Conservative, Labour and Liberal Democrat MSPs would vote against another referendum, but would find themselves outnumbered.

Ruth Davidson said Ms Sturgeon had "made it clear she wants to take Scotland back to yet more uncertainty, more division and more constitutional upheaval" and accused her of failing to respect the 2014 result when two million people rejected independence.

The Scottish Tory leader added: "This isn't the action of a First Minister of Scotland but an SNP fundamentalist who puts independence first, last and always."

Kezia Dugdale, the Scottish Labour leader, accused Ms Sturgeon of putting independence over education, health or tackling poverty.

She said: "Nicola Sturgeon’s top priority is to divide our nation once again. But our country is already divided following the Tories’ reckless Brexit gamble and we should not be seeking further divisions.

"Our economy is in trouble, and the last thing we need is the uncertainty of another independence referendum. In her speech to the SNP conference, Nicola Sturgeon had an opportunity to tell the country how she will face the challenges of the future. Instead, she resorted to an argument of the past."

The UK Government has previously rejected the suggestion Scotland could be handed a bespoke Brexit deal, with Ms May telling the Tory conference earlier this month the nation would "leave the European Union as one United Kingdom.”

Downing Street said the independence question had been “addressed in 2014”.

Referring to Ms Sturgeon’s demand for trade and immigration powers, a spokeswoman said it was not a question of "dismissing them outright" but it raised fundamental questions which would need to be "looked at carefully" given there was a clear devolution settlement.

Business leaders in the CBI urged the Scottish and UK governments to work together on the best possible deal in EU talks, but dropped their previous knee-jerk hostility to a referendum.

Hugh Aitken CBE, CBI Scotland Director, said: “A second Scottish Independence referendum is rightly a matter for the Scottish people and their elected representatives.”