A new poll on Scottish independence has been published by Progress Scotland showing 51% of voters wish to remain part of the Union.

The survey, commissioned by the pro-independence group, found 40% of voters who expressed an opinion support independence compared to 51% of voters who would rather remain part of the union.

Of those who voted for independence in the 2014 referendum, 16% now say they “completely support Scotland staying part of the UK”, whereas 4% of No voters polled now fully back Scotland becoming independent.

READ MORE: Scots' support for remaining in the UK on the wane

HeraldScotland: Camley's Cartoon: The tree that's as old as the Union.Camley's Cartoon: The tree that's as old as the Union.

Some results from the poll, including the issue of Brexit becoming the most important issue influencing views on independence, were released in the lead-up to the SNP’s party conference.

READ MORE: Poll: Support for EU and holding a new Indyref rises

On the issue of the question used in any future referendum, 70% said it should be the same as in the 2014 referendum – “Should Scotland become an independent country?” with options of yes or no.

A total of 17% of those surveyed in the Survation poll for former SNP depute leader Angus Robertson’s research group Progress Scotland think the question should be changed and 13% said they did not know.

The full findings  – which were published on the Survation website on Monday  –  revealed 37% of voters fully back Scotland staying part of the UK, 11 points higher than those who completely support Scotland becoming independent.

Reacting to the survey, Scottish Conservative constitution spokesman Adam Tomkins said: “It’s no wonder these independence campaigners want to keep the results of this poll quiet.

“Progress Scotland aren’t usually slow to trumpet their findings so it’s interesting that they’ve been so secretive about this particular survey.

“Like the vast majority of polls, it reveals again that more Scots want to remain in the UK than to leave it.

“And, far from gaining momentum, it seems the Yes campaign is losing supporters at a higher rate than it’s gaining them.”

According to the poll, more than half of Scots (55%) think there will be another vote on independence within the next two years.

First Minister Nicola Sturgeon used her address to the SNP conference in Aberdeen earlier this month to insist a second referendum “must” take place next year.

Just over a third (35%) of those polled said another ballot was “unlikely” in the next 24 months, while 10% said they did not know.

Pamela Nash, chief executive of the pro-UK group Scotland in Union, claimed the poll  of more than 2,000 adults had  “backfired spectacularly”.

READ MORE: Johnson may have made independence 'completely inevitable' says Nicola Sturgeon 

She said: “No matter how Progress Scotland tries to spin the findings, its own figures show that massive numbers of former Yes voters have changed their minds and would now vote to stay in the UK.”

Scottish National Party Conference 2017Angus Robertson addresses delegates at the Scottish National Party conference at the SEC Centre in Glasgow. (Jane Barlow/PA)

At the time of the partial publication of the survey, managing director of Progress Scotland Angus Robertson said: “These findings illustrate the significant impact that Brexit is having on the views of open-minded people towards Scottish independence.

“These are just the initial findings from the inaugural large-scale opinion poll for Progress Scotland and more results will follow.

“This is just the beginning of our work, which over time will allow us to better understand an ever-growing number of people in Scotland who are open-minded towards independence.”

Keith Brown, SNP depute leader, said:  “People in Scotland overwhelmingly oppose leaving the EU and it’s abundantly clear that views are changing on independence as voters look to escape this Brexit nightmare.

“With Westminster in chaos and Boris Johnson in Downing Street, more and more people are ready to listen to the case for a progressive, independent Scotland within Europe.

“The people of Scotland deserve the choice of a better future than the Brexit Britain being imposed on us.

“Be in no doubt, a referendum is just round the corner and the people of Scotland will make their voices heard.”

*This article has been amended to reflect the previous Progress Scotland poll*