Brexit is now the most important issue for Scots when considering if the country should be independent, according to a new opinion poll.

More than two-fifths (43%) of voters cited this as one of the three key issues they would consider when deciding if Scotland should be independent – just ahead of the 42% who said the economy was the most pressing factor.

In 2014, the year of the independence referendum, the future of the economy was given as the main concern by 46% of voters, with EU membership only ranking as the sixth most important issue.

The findings were revealed in a poll of more than 2,000 people in the first piece of research carried out for Progress Scotland, the organisation set up by former SNP depute leader Angus Robertson.

He established the company with polling expert Mark Diffley with a view to examining how public opinion is changing across Scotland.

The research, carried out by Survation between March 15 and 21, questioned 2,041 adults on their views.

Among those Scots who classed themselves as “undecided” about independence, almost two-thirds (63%) said Brexit made Scotland leaving the UK more likely.

Nearly half (45%) of this group said Brexit had changed their view on independence – with 56% saying if the UK was forced to quit the EU without a deal they would be more likely to vote for independence in a second Scottish referendum.

Two-thirds (66%) said if Scotland was to become an independent country it should be a full member of the European Union.

Mr Diffley said: “Since June 2016, politics across the UK has been dominated by the issue of Brexit.

“It is therefore unsurprising that, on the day that the UK had been due to leave the EU, new polling highlights the pivotal role that the issue of EU membership and Brexit is likely to play in any future Scottish independence referendum.”

He said the poll “makes for interesting reading in understanding how voters view the relationship between Brexit and independence”.

Mr Diffley added: “The importance of the EU as an issue which drives opinion on independence has doubled – 22% of voters put EU membership in the top two or three issues which determined their vote in 2014.

“Now, that figure is 43%, making it the single most important issue for voters in another referendum.

“The poll provides further evidence of how the issue of the EU might impact on voters who have no firm position on the independence question.

“The poll suggests that this cohort of ‘open-minded’ Scots has both strong views on the EU and is reassessing its views on independence in light of the Brexit debate.”

Progress Scotland managing director Angus Robertson (Jane Barlow/PA)

Mr Robertson, the managing director of Progress Scotland, 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.”

SNP depute leader Keith Brown welcomed the research, which he said “shows that people are increasingly concerned that they face being taken out of the EU against their will and are open to changing their view on independence as a result”.

But Pamela Nash, chief executive of the pro-UK campaign group Scotland in Union, said the poll had “inadvertently revealed the strength of support for remaining in the UK” – with 40% backing this completely, compared to the 24% who completely support independence.

She also claimed it showed “large numbers who voted Yes in 2014 have now changed their minds”.

Ms Nash said: “Unsurprisingly, Brexit is a key issue for voters. So while this poll is very encouraging, it must also serve as a reminder that those of us who believe in solidarity and oppose nationalism, that we must continue fighting for Scotland’s place in the UK.

“The future of the economy remains a vital issue for voters, and independence would be eight times as costly for our economy as even the worst-case Brexit.”