THE Scottish Government will this week reach out to opposition leaders to back calls for Boris Johnson to consent to indyref2 after Scotland’s largest trade union came out in favour of holding another vote, the Sunday National can reveal.

Unison yesterday voted in favour of a second independence referendum and for the relevant powers to be transferred from Westminster to Holyrood.

The move comes as Nicola Sturgeon’s plans to build consensus with Jackson Carlaw, Richard Leonard and Willie Rennie.

In a key speech on Friday, the First Minister outlined proposals for a constitutional convention with the aim of building support for another independence referendum.

The Sunday National has learned the process will begin this week when the other party leaders in Scotland will be invited to become involved.

READ MORE: Unison votes to back calls for second independence referendum

Yesterday the call for a referendum was given Unison’s backing at a meeting of the union’s Scottish council.

A motion was passed demanding that the power to hold a vote be transferred from Westminster to Holyrood. Boris Johnson has so far refused to countenance another referendum.

Unison’s Scottish convenor Lilian Macer said: “This in no way pre-determines the views our members may take in the event of an independence referendum, but they should have the opportunity to express their views.

“Unison Scotland defends public services and those who deliver them and it is imperative that we explore the full range of options available to the people of Scotland.”

On Wednesday, the Scottish Parliament voted to hold an independence referendum this year – and a new poll by YouGov showed majority support for independence at 51%.

Separately, a poll by Survation found 61% believe the Scottish Parliament should determine the timing of a fresh referendum.

READ MORE: SNP MSP: "For us to win the fight for indy, we need to talk to more people"

Unison’s decision follows a similar call by Scottish Trades Union Congress (STUC) General Secretary Grahame Smith, and cross-party voices including senior Labour MSPs and MPs who have called for the Scottish Parliament to have the power to hold an independence referendum.

“There is now an unstoppable momentum behind a fresh independence referendum,” said SNP Depute Leader Keith Brown MSP.

“Scotland voted overwhelmingly to reject Brexit but we have been dragged out of the EU against our will by a Tory Government with no mandate here. The people of Scotland must have a choice over our future – so we can remain at the heart of Europe as an equal and independent country.

“Unison, Scotland’s biggest trade union, is the latest respected body to support a transfer of powers so the Scottish Parliament can hold a fresh referendum at a time of its choosing. The democratic right of the people of Scotland to determine our own future cannot be ignored by Westminster.

“And the Constitutional Convention announced by the First Minister on Friday will provide an opportunity for organisations such as Scotland’s trade unions to come together with elected politicians around that democratic right.

“The SNP won a landslide victory at the General Election on a cast-iron mandate to hold an independence referendum. The more Boris Johnson tries to ignore Scotland’s democratic mandate to choose our own future the more support for independence will continue to grow.”

The Scottish Greens also welcomed Unison’s independence referendum decision. Co-leader Patrick Harvie (above) said:

“Today’s decision by Unison to back an independence referendum is a totemic moment for the independence movement.

“Unison, Scotland’s largest trade union, represents members of different party political persuasions, but its decision today to back an independence referendum, at a time to be determined by the Scottish Parliament, recognises the democratic deficit that we currently face. This can only be resolved by putting the question of Scotland’s future back to the people.

READ MORE: Internal critics reject Nicola Sturgeon's indyref2 plan

“Now that Scotland has been dragged out of the EU against our will, it’s clear that more and more people are coming to the conclusion that Scotland’s future is as an independent European nation.

“An opinion poll published just this week shows that there is now majority support for independence, with many people who had previously voted No and subsequently to remain now supporting independence.

“Scottish Greens will continue to be at the forefront of the campaign for Scotland to take its place as an independent nation in the EU.”