Labour will invite the SNP to work with them to make devolution work if Scotland votes against independence in the referendum.

Shadow foreign secretary Douglas Alexander is expected to say in a speech tomorrow that it will be important to ensure Scotland does not "divide more deeply" after the vote on September 18.

He will say the choices made after the referendum will help shape the new Scotland almost as much as the vote itself.

Mr Alexander will declare that he firmly believes Scotland will choose to stay together with its neighbours across the UK, but will call on supporters of different parties to work together whatever the outcome.

He will say: "If Scotland votes to stay with its neighbours, I would urge those who voted Yes to then choose to join us to work together in the task of making devolution work, not proving devolution wrong.

"Indeed I believe that the choice to stay together will create an opportunity for politicians to lay the ground for a way of doing politics differently.

"Elsewhere, I have argued that the establishment of a national convention could be one way to chart a new course for an old nation.

"Others will have other ideas, but the tasks of bringing a divided nation together will be real, urgent, and important."

Mr Alexander will make his speech in Edinburgh tomorrow to mark the 20th anniversary of the death of Labour leader John Smith and the 15th anniversary of the first sitting of the Scottish Parliament.

He will call for a "politics of opponents, not enemies" inspired by Mr Smith's example, and a "respectful discourse of political discourse" rather than a politics that "descends into personal destruction".

Mr Alexander will say that the result of the referendum will leave Scotland divided, with a significant minority of the population feeling disappointed.

He will set out the challenge which will be to ensure that Scotland comes together whatever the outcome of the vote and does not divide more deeply.

He will say: "When, as I firmly believe in September, Scotland chooses to stay together with our neighbours across the UK, that will see the rejection of the defining mission of the present Scottish Government and indeed of the Scottish National Party.

"Indeed they will face an existential issue if their Raison d'etre is rejected by the sovereign will of the Scottish people.

"But in every crisis there is an opportunity - and a choice not defined by difference or grievance, but by possibility, potential and hope."

SNP MSP Bruce Crawford said: "We are entirely focused on achieving a Yes vote in September in the best interests of Scotland - and are confident of doing so with the polls now virtually neck and neck. We are equally clear that after a Yes vote we will pursue an inclusive and participative approach, both to the independence negotiations and developing a written constitution for Scotland.

"Canon Kenyon Wright - one of the architects of Scottish devolution - has today made clear his belief that a Yes vote is the only way to 'allow the new Scotland of our hopes to emerge' - and that this cannot be delivered within the UK.

"And the fact remains that only a Yes vote can guarantee further powers - the No parties have nothing substantial to offer Scotland. As Professor John Curtice has said, Labour's Devolution Commission proposals 'fall well short' of the powers the majority of people in Scotland would like.

"We must vote Yes in September to guarantee the powers Scotland needs to thrive. And with independence we will no longer have to put up with governments we didn't elect and polices such as the unfair bedroom tax and Trident nuclear weapons dumped on the Clyde."