Alex Salmond will mark St George’s Day today by promising that an independent Scotland would champion the North of England to balance the economic might of London.

Speaking in Carlisle, Scotland’s First Minister will insist that the “social union” between the people of the four members of the United Kingdom would remain if the Scottish people vote to leave it in their September referendum.

In what may be seen as a provocative speech, Mr Salmond will announce that after a Yes vote, the Scottish Government would hold a series of “Borderlands” forums on economic co-operation with councils and business leaders from the North of England. He will describe this as “a practical demonstration of co-operation” and of a partnership strengthened by an outward-looking Scotland. “An independent Scotland will be an economic counterweight to London and the South-east of England – causing a much-needed and fundamental rebalancing of these islands,” the SNP leader will say.

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“An independent Scotland will work in collaboration with our friends and colleagues in the North of England to improve economic circumstances and job opportunities for all our citizens.”

Mr Salmond will tell his English audience: “The ties that bind the nations of these islands will continue and flourish after Scotland becomes independent. You will remain Scotland’s closest friends, as well as our closest neighbours… People would still live in Annan and work in Carlisle, or live in Penrith and work in Lockerbie. Friends and family would continue to visit each other. We would still watch many of the same television programmes.”

Mr Salmond will also claim that an independent Scotland would have strong trade and transport links with England – and share the same currency, even though all three main parties at Westminster have ruled out a currency union if the SNP secures a Yes vote.

Gordon Brown said yesterday it made “no sense whatsoever” for Scotland to break its political links with England. The former Prime Minister instead urged people north of the border to vote No in September in a bid to build a “stronger Scotland”. The former Labour leader made the plea as he gave his first speech as part of the cross-party Better Together campaign. David Cameron will use his St George’s Day message to trumpet the benefits of Scotland staying in the UK. He will say: “I want us to reflect on one of England’s greatest achievements: its role in the world’s greatest family of nations – the United Kingdom. So let’s prove we can be proud of our individual nations and be committed to our union of nations. Because no matter how great we are alone, we will always be greater together.”

Allies denied the PM’s decision to issue a patriotic message was a response to the rise of the UK Independence Party, saying he had delivered one last year. But Mr Cameron, who will fly the flag of St George over Downing Street today, will say England’s national day has been overlooked for too long. “There’s much to celebrate,” he will say.