NICOLA Sturgeon will not be given permission for a second referendum until there is “clear political and public agreement” to hold one, the Prime Minister and her allies said yesterday.

Setting out a series of tests which appeared designed to block a vote in the current Scottish Parliament, senior Tories said it would be “unfair” to have one until well beyond Brexit.

In a message intended to resonate with the prevailing public mood against a pre-Brexit referendum, Mrs May said repeatedly in a TV interview: “Now is not the time.”

SNP and Greens are expected to back Ms Sturgeon’s plan to request referendum powers from Westminster, known as a Section 30 order, in a vote at Holyrood on Wednesday.

Mrs May and colleagues said the request will be refused despite majority support at Holyrood, setting up the biggest constitutional crisis since the advent of devolution in 1999.

Making it clear the coming Brexit negotiations were her priority, not fighting another referendum, Mrs May told ITV: ''Right now we should be working together, not pulling apart.

''We should be working together to get that right deal for Scotland, that right deal for the UK.

“That's my job as Prime Minister and so for that reason I say to the SNP: now is not the time."

She added: "It wouldn't be fair to the people of Scotland because they'd be asked to make a crucial decision without the necessary information, without knowing what the future partnership will be or what the alternative for an independent Scotland would look like."

At a press conference in Edinburgh later, Scottish Secretary David Mundell and Scottish Conservative leader Ruth Davidson flatly rejected the timetable set out by Ms Sturgeon on Monday of a referendum between autumn 2018 and spring 2019, or shortly after.

Voters would know the implications of Brexit by then, the First Minister had said.

But Mr Mundell said such a referendum would not meet the agreed criteria for the 2014 referendum, set out in the Edinburgh Agreement, for the vote to be “legal, fair and decisive”.

He said: "The proposal brought forward is not fair, people will not be able to make an informed choice. Neither is there public or political support for such a referendum.

"Therefore we will not be entering into discussions or negotiations about a Section 30 agreement and any request at this time will be declined."

Ms Davidson said the SNP needed to “earn the right” to hold a second referendum.

Her spokesman later suggested this meant securing an unambiguous mandate in another Scottish election by winning a majority of seats.

Saying Ms Sturgeon’s timetable would be “unfair to Scottish voters”, Ms Davidson said: “On the most important political decision a country can make we would be voting blind.

“People should only be asked to make a judgement about whether to leave or remain within a 300-year old Union of nations when they have seen for themselves how that Union is functioning following Brexit.

“They should also know what the alternative entails, and we have seen no clarity from the SNP on even the basic questions of their proposition.

“But I believe there is another fundamental reason why now is not the right time to take Scotland back to the precipice.

"And that is because there is no clear political or public consent for this to take place.

“The country – and our Parliament – is divided not over just the question of independence, but over whether we should even hold a referendum or not.”

Although neither Mr Mundell or Ms Davidson ruled out a referendum in the final two years of the Scottish Parliament after Brexit, their tests appeared nigh impossible for the SNP to meet, as they included consensus on an issue is inevitably divisive.

Ms Davidson said: “At an absolute minimum... there should be agreement across political parties and from the public at large, that it is right and fair for such a referendum to proceed.”

She added: “If the SNP insists on pressing ahead, we will argue that a referendum cannot happen when the Scottish people have not been given the opportunity to see how our new relationship with the EU is working. And until there is clarity over the alternative.

"And we will maintain that it should not take place when there is no clear public or political consent for it to happen."

Ms Davidson’s spokesman later said voters should not only be given time to absorb the final Brexit deal, but also the new constitutional landscape across the UK after powers were repatriated from Brussels to Westminster and then redistributed throughout the UK.

Such a process could take several years and a new Scotland Act, given the experience of devolving more powers to Holyrood after the 2014 referendum.

Tory MSP Murdo Fraser said Mrs May was in tune with “the majority of people in Scotland”.

He told BBC Radio Scotland: "What she's trying to do is create a stable settlement in the UK and some stability at a time that the UK government is involved in what will inevitably be a very difficult negotiation for Brexit which is a major challenge for this country. An independence referendum while that's going on is going to add an extra layer of uncertainty and disruption."