Gordon Brown has said the Union has never been at a more perilous moment in his lifetime as he urged Boris Johnson to change his approach to Scotland to keep the UK whole.
In an interview with The Telegraph, former prime minister Mr Brown warned that Scottish independence would not be prevented simply by putting more British flags up in Scotland.
He called for the House of Lords to be replaced with a Senate of the UK’s nations and regions, noting that currently peers overwhelmingly come from south-east England, and criticised Mr Johnson for not doing more in his press conferences to address people in Scotland and Wales.
The former Labour leader said the UK Government should "get round a table" with the Scottish government for a "discussion" about a second independence referendum.
Mr Brown was speaking for a Telegraph documentary about the independence debate and the SNP’s calls for another referendum.
During the 2014 referendum, which saw Scots vote to remain in the UK by 55 per cent to 45 per cent, Mr Brown made a series of impassioned interventions near the end of the campaign which were credited with boosting the pro-UK side.
Asked earlier this month, whether the UK had ever been at a more perilous point in his lifetime, the 70-year-old said: "No, of course not.
"We have opinion polls that are registering support for independence, we’ve got a party that wants independence that’s running the Scottish government, all because of mistakes that have been made by either one or two of the Unionist parties. And so the Union is in difficulty.
"But it will require statesmanship and leadership to be able to sort out the problems that exist and to understand that there’s no one silver bullet.
"You know, labelling a road British is not going to save the Union. Putting up more flags is not going to save the Union.
"Bypassing the Scottish government and saying we’re not talking to them because we don’t recognise them as legitimate will only alienate Scottish opinion. So you’ve got to look at the causes of nationalism."
His last comment was aimed at Downing Street and the "muscular unionism" approach, in part inspired by the Leave campaign’s victory in the Brexit referendum, which has been followed at times to sell the UK’s benefits north of the border.
Mr Brown said he wanted Mr Johnson to adopt a more engaged approach, adding: "His interest in Scotland is very limited. He visits here almost once, twice a year perhaps. He doesn’t address his remarks when he’s doing press conferences on health, for example, to anything other than England.
Gordon Brown said Boris Johnson had 'limited interest' in Scotland
Credit: Jane Barlow/PA
"He doesn’t talk about what’s happening in Scotland or Wales. There seems to be very little communication between him and the Scottish government."
One big constitutional reform championed by Mr Brown is scrapping the Lords in its current form. With Number 10 reluctant to act, he said: "A second chamber in any country has got to have a purpose.
"The House of Lords defends itself as a revising chamber, but it’s completely unrepresentative of the public and it’s got worse in the last 10 years. People actually think the House of Lords is extremely remote from everyday life."
He said he wanted to see it become a Senate where not just the four nations of the country but also its regions are fully represented, adding: "Manchester, Liverpool and Newcastle – they all want a voice. If you look at the House of Lords at the moment it’s basically a South East body."
On a second referendum, Mr Brown declined to offer an opinion about whether it should be held but called for talks rather than the current stand-off. "I’m saying there’s got to be a discussion. You can’t sort this out without getting round the table," he said.
And what if there is another referendum? Is he confident that, in five years, Scotland will still be part of the UK?
"I believe we can win a referendum if there was to be a referendum. I believe that the case for co-operation across the United Kingdom is very strong," he said. "I think most people in Scotland would actually respond to a message that Scotland could feel comfortable in a reformed United Kingdom.
"But look, the people in power at the moment, there’s a tremendous responsibility on their heads because it is they who will decide whether the Union survives by either the failure to act or by doing the wrong things."