Former prime minister Gordon Brown has defended Scotland's continued place in the UK as key to maintaining social justice.
Scottish values helped to form the Union, he said before a speech in Kirkcaldy in his Fife constituency.
"I believe that as Scots we can and should take pride in our long-term and enduring Scottish commitment to social justice and strong communities," the Labour MP said.
"Indeed we should be proud that over the last century these Scottish values, supporting justice and community, have shaped the Union. These values have led to the pooling and sharing of risks and resources across the UK and the creation of equal social, economic and political rights for all citizens, irrespective of ethnicity.
"They have narrowed the inequalities between the nations of the United Kingdom so that, unlike other neighbouring nations in Europe and elsewhere, there is just a 4% difference between Scottish income per head and English income per head."
Mr Brown said there are gaps in SNP policy about how current arrangements can be replaced.
"Under their plans, all the decisions in an economic crisis would be made for Scotland by a separate government and a central bank from the rest of the UK: a form of self-imposed imperialism that smacks of 19th-century colonialism and is far from the modern principles we should aspire to," he said.
"But today I want to say that there is a third gap in policy, beyond the problems they have on Europe and on monetary policy. The absurdity of their policy is such that while they claim independence will give them more freedom over fiscal policy, they have had to admit that they would need to make a fiscal deal with England."