A draft bill on a second independence referendum has been published by the Scottish government after the first minister, Nicola Sturgeon, pledged to hold a new poll in the event of a hard Brexit in a direct challenge to Theresa May.

The draft legislation, which was formally unveiled by the constitution secretary, Derek Mackay, despite the Scottish parliament being in recess until next week, sets out proposals for the rules governing the campaign, the conduct of the poll and how votes are counted.

Mackay said the proposed franchise would be the same as for the Scottish parliament. “That will mean two important groups of people would have a voice denied to them in the recent referendum on EU membership: 16- and 17-year-olds and citizens of EU countries who have made Scotland their home.”

The eight-page document proposes that any referendum would be run in a way similar to 2014, using the same yes/no question: “Should Scotland be an independent country?” It also suggests that the vote would similarly not be subject to any minimum turnout requirement or an approval threshold.

Sturgeon said she would put forward proposals for maintaining Scotland’s position in the single market. Photograph: Murdo Macleod/The Guardian

As the bill was published, Sturgeon said: “We will continue to work UK-wide to seek to avert a hard Brexit and we will also bring forward proposals that seek to protect our place in the single market, even if the rest of the UK leaves.

“However, if we find that our interests cannot be properly or fully protected within a UK context then independence must be one of the options open to us and the Scottish people must have the right to consider it.”

She added that any decision on holding a referendum, including the timing of it, would be for the Scottish parliament – where a pro-independence majority exists between the SNP and the Scottish Greens – to take. Despite May’s stated intention to oppose another independence poll, Holyrood would then ask the UK government to grant a section 30 order to allow the vote to take place.

Sturgeon, who will next meet May in London on Monday with other heads of devolved governments, has said she will put forward specific proposals in the coming weeks for maintaining Scotland’s position in the single market even if the rest of the UK leaves, as well as pushing for substantial additional powers for Holyrood as part of the UK’s article 50 negotiations, including over international trade deals and immigration.

In her foreword to the consultation, which will run until 11 January 2017, Sturgeon writes: “In May 2016 the current Scottish government was elected with a clear mandate that the Scottish parliament should have the right to hold an independence referendum if there was clear and sustained evidence that independence had become the preferred option of a majority of the Scottish people – or if there was a significant and material change in the circumstances that prevailed in 2014, such as Scotland being taken out of the EU against our will.”

She adds: “The UK government’s recent statements on its approach to leaving the EU raise serious concerns for the Scottish government. We face unacceptable risks to our democratic, economic and social interests and to the right of the Scottish parliament to have its say.

“Indeed those statements contradict the assurances given before the independence referendum in 2014 that Scotland is an equal partner within the UK and that a vote against independence would secure our EU membership.”

But the Scottish Labour leader, Kezia Dugdale, described the draft bill as “irresponsible economic vandalism”, warning: “Our economy is in trouble following David Cameron’s reckless Brexit gamble, and the very last thing we need is more uncertainty for employers.”

And speaking before the publication, the Scottish Conservative leader, Ruth Davidson, vowed that her party would fight proposals for a second referendum “every step of the way”.

Dugdale has also written to the Scottish parliament’s presiding officer, Ken Macintosh, asking for clarification over how the SNP’s plans will be examined, arguing that the SNP is trying to dodge scrutiny by publishing the consultation during parliamentary recess.