If Scotland becomes independent during Boris Johnson’s premiership, that will be his lasting legacy, former prime minister Gordon Brown has said.

The argument over Scottish independence has intensified in recent days after the SNP’s landslide victory in the Holyrood election, which also produced the largest pro-independence majority in the Parliament in the history of devolution.

The Prime Minister has since stood by his pre-election position, saying the focus should be on the recovery from Covid-19 and not on another independence referendum.

If Boris Johnson becomes the Prime Minister who loses Scotland and sees the end of the United Kingdom, that's all he will be remembered for

Speaking on Times Radio on Wednesday, Mr Brown claimed Mr Johnson’s lasting legacy would be losing Scotland if the country becomes independent, adding he believes the PM does not “understand” the union.

He said: “The problem for Boris Johnson is, I think he had one sentence in his speech yesterday, the Queen’s Speech, about the union itself.

“I don’t think he’s thought about it, I don’t think he understands it, I think he’s got to start beginning to understand it.

“He’s a historian, he must remember that Lord North was the prime minister who lost America and that’s all he’s remembered for, if Boris Johnson becomes the Prime Minister who loses Scotland and sees the end of the United Kingdom, that’s all he will be remembered for.

“We need to give some attention to this issue, and we need to do it pretty urgently.”

Mr Brown, who left office in 2010, has previously railed against the “muscular unionism” of the current Westminster administration, which has said it would like to finance projects in Scotland through local authorities as opposed to the Scottish Government – an approach widely criticised by the SNP during the latter part of the last Holyrood term and in the election campaign.

More people in Scotland embrace their Scottish identity first before their British identity, according to Mr Brown, and he said you can be a “patriotic Scot” while also supporting the union – but he added the union should be one where “people are co-operating with each other rather than, as Boris Johnson seems to be doing, putting people at permanent war with each other”.

Mr Brown said about 40% of people in Scotland are not convinced either of the case for the union or for independence.

He called for a permanent forum of all the nations and regions to be set up where issues can be discussed, including the leaders of the devolved administrations and English mayors.

“Then we’d get a sense that we were talking about issues that have got to be sorted by all these people working together,” he said.

“Bring people in, that would be the first step, but that’s only the first step to trying to sort out what is a major problem that I think the United Kingdom now faces.”

Following the Holyrood election, Mr Brown’s think tank Our Scottish Future became a “campaigning movement” for Scotland to remain in the UK, but also the reform of the union.