The chancellor has warned that four years of constitutional fighting over separation would damage Scotland's economy.

Alistair Darling said in a speech on Thursday night that the nation should focus on meeting the "urgent" challenges of globalisation.

The Edinburgh MP said the nationalist administration in the Scottish Parliament would be be making a "profound mistake" if it concentrated on pursuing independence.

"I believe that Scotland faces a stark choice today," he said.

"Is Scotland's priority constitutional change, or the urgent task of addressing the challenges and opportunities posed by globalisation as we try to secure a sustainable, prosperous future for Scotland and for Britain?

"I believe it would be a profound mistake to spend the next four years in constitutional conflict north and south of the border when we need to meet the economic challenges we face.

"Go to India and China - these economies are growing ever year."

He argued that even if separation was achieved, Scotland would suffer outside the Union.

"In 10 out of the 11 main industry sectors, Scotland's trade with England is larger than for the rest of the world put together," the chancellor pointed out.

"The scale of this trade is a demonstration of the benefits of an open, single economy built up over hundreds of years. We need to think long and hard before putting that at risk."

And Darling said the SNP would be wrong to rely on oil revenues.

"Those who think we can build an economy on the value of a commodity such as oil are simply failing to face the challenges of the 21st century, especially when it is a very finite resource, perhaps 30 years left," he argued.

"The only commodity which ensures continuing economic prosperity into the future is the skills of our people."

"In the next few decades we will see more and more people and countries working together realising their interdependence," he added.

"They'll want to be closer together not further apart."