NICOLA Sturgeon will this week make a formal request to the Prime Minister for Holyrood to be given powers to hold a new independence referendum, saying it would be “democratically indefensible” for it to be refused.

MSPs voted by 69 to 59 to give the First Minister a mandate to seek permission from the UK Government for a vote to take place between the autumn of 2018 and spring 2019.

A constitutional clash between the Scottish and UK Governments is now likely as Theresa May has said she will block another referendum – stating “now is not the time” – while David Mundell suggested last night that it could be a considerable length of time – well beyond 2019 – before consent could be given.

The Scottish Secretary appeared to deny the 18-month to two-year Brexit timetable Sturgeon said May had given her on Monday, and said the UK Government would not “be entering into any negotiations at all until the Brexit process is complete” possibly after Brexit is implemented. “Now’s the time for the Scottish Government to come together with the UK Government, to work together to get the best possible deal for the UK, and that will mean for Scotland, as we leave the EU,” Mundell said.

“We’re not entering into negotiations on whether there should be another independence referendum during the Brexit process. We don’t have a crystal ball as to how long that process will take. We don’t recognise, for example, 18 months as being a key point in the journey.

“It will be a journey that will involve the negotiations with the EU, it may be a journey that involves transitional measures, it may be a journey that will involve significant implementation time.

“It’s not appropriate to have a referendum while people do not know what the future relationship between the UK and the EU is and they won’t know that until the Brexit process is complete.”

A two-day debate started at Holyrood last week but was suspended on Wednesday after the terror attack at Westminster.

Yesterday’s vote came the day after Sturgeon met with May in Glasgow, and the day before the process for leaving the European Union will be formally triggered by the PM.

The First Minister has insisted her referendum timetable would allow voters in Scotland to make an informed choice when the terms of the UK’s exit deal become clear and before it is “too late to choose our own course”.

Speaking before the leaders’ meeting on Monday, May said her position will not change, arguing that a vote within Sturgeon’s proposed time frame would be unfair to voters and come at a time when the focus should be on securing the best Brexit deal for the whole of the UK.

However, after their meeting the First Minister said the Prime Minister had no rational basis for opposing an independence referendum as she had told her the Brexit process and any new arrangement the UK had with the EU would be finalised within two years.

Yesterday, Sturgeon said she would delay making the Section 30 request – the mechanism for the transfer of powers to hold the referendum – until “later this week” after May had triggered Article 50.

She said she “hoped the UK Government would respect the will of the Scottish Parliament’’, but if it does not she will set out her next steps in Holyrood after the Easter recess.

Sturgeon said: “It is now the will of Scotland’s democratically-elected national Parliament that discussions should begin with the UK Government to enable an independence referendum to be held.

“Today’s vote must be respected. The mandate for a referendum is beyond question, and it would be democratically indefensible – and utterly unsustainable – to attempt to stand in the way of it. We will now act on the mandate given to us by Parliament by making a formal approach to the UK Government within the next few days, after Article 50 has been triggered.

“This is, first and foremost, about giving the people of Scotland a choice on this country’s future.

“The Prime Minister says that now is not the time for a referendum. I agree with that, which is why I have indicated a timescale no earlier than 18 months from now, when the terms of Brexit are clear – something the PM has now indicated she agrees with.

It is up to the UK Government to now make clear when they consider a referendum would be appropriate.”

It was not clear last night what the First Minister’s next step would be, but it is thought unlikely she would settle for an advisory referendum, meaning it is more likely to involve plans to push forward with a referendum bill.

A UK Government spokesman said: “The Prime Minister has been clear that now is not the time for an ind-ependence referendum, and we will not be entering into negotiations on the Scottish Government’s proposal. At this point, all our focus should be on our negotiations with the European Union, making sure we get the right deal for the whole of the UK. It would be unfair to the people of Scotland to ask them to make a crucial decision without the necessary information about our future relationship with Europe, or what an independent Scotland would look like.

“We have been joined together as one country for more than 300 years. We’ve worked together, we’ve prospered together, we’ve fought wars together, and we have a bright future. At this crucial time we should be working together, not pulling apart.”

Sturgeon’s minority Scottish Government won the vote following an extended debate thanks to support from the Scottish Greens.

Last night the Greens welcomed the vote backing the request for a Section 30 order, and support for their amendment calling for EU citizens and 16 and 17-year-olds to have the opportunity to vote in a new independence referendum – something they were denied to them in last year’s EU referendum.

Ross Greer, the party’s external affairs spokesman, said a referendum would give people in Scotland a choice between independence and walking off a “hard Brexit cliff”. He said: “It should be our responsibility, as those elected by the people of Scotland, to fight for their right to choose their own future. During a period where 27 other EU nations ... will have a say on Scotland’s future it is only right that the people who live here have theirs as well.”