Most voters are in favour of the Union but believe Brexit has made the break-up of the United Kingdom more likely, polling has found.
In England, 68% of adults backed the UK status quo followed by 66% in Wales, 59% in Northern Ireland and 52% in Scotland, according to the ICM research.
But across the four nations, up to six out of 10 voters said Britain’s exit from the European Union had increased the prospect of the UK splitting up.
The study for Policy Exchange comes ahead of its conference on the union and unionism, which includes speeches from Environment Secretary Michael Gove, DUP leader Arlene Foster and Ruth Davidson, leader of the Scottish Conservatives.
Dean Godson, director of the think tank, said: “Support for the Union is strong – but people are understandably nervous about the future.
“The UK needs a ‘new Unionism’, one based not just on the constituent parts of the United Kingdom, but on the regions and peoples within them.
“A new Unionism would not deny the difficulties faced by the United Kingdom, but Brexit also provides an opportunity for a reboot of one of the most successful nation states in modern history.”
Concerns about a Brexit-fuelled break-up of the UK were most pronounced in Northern Ireland where 60% of voters believed it was likely to happen.
Failure so far to find a solution to the Irish border issue has proved the key stumbling block in exit negotiations.
Scotland followed on 59%, England on 58% and 54% in Wales.
Ms Davidson said on Sunday the UK should become less London-centric to strengthen and protect the union.
She called for major institutions – such as the British Museum – to consider setting up elsewhere in the UK, as well as for most fishing infrastructure to be moved to Scotland.
First Minister Nicola Sturgeon promised to “restart the debate” on Scottish independence with the publication of her party’s long-awaited growth commission this Friday.
ICM polled 533 people in England, 514 in Scotland, 513 in Wales and 500 in Northern Ireland between May 15 and May 17.