The erection of border posts between Scotland and the rest of the UK would also be “unavoidable” under Nicola Sturgeon’s plans to retain freedom of movement with the rest of the EU while this comes to an end elsewhere in the UK under Brexit.
The First Minister is preparing to unveil her long-awaited summer independence push later this week. But it will come after official figures last week revealed that the oil crash has left Scotland with a £14.8 billion deficit between public services and taxes raised to pay for them.
The former Labour leader called for a new “home rule” deal for Scotland in the aftermath of the Brexit vote as he addressed the Edinburgh International Book Festival. He warned that the post-referendum tax and welfare powers coming to Holyrood now do not go far enough.
The SNP has “no solution” over the currency to be used under independence, he said, or the pooling and sharing of resources with the UK to protect Scots’ pension levels.
Mr Brown said: “I don’t think they have any solution to the fiscal gap which is around £15 billion – big enough to double the rate of income tax in Scotland if you wanted to maintain the level of services.
“I don’t think they’ve got any answers on the border either - because if you want a separate migration policy in Scotland, which is what Nicola Sturgeon says she wants – she wants people to come into Scotland under different rules from the United Kingdom – then how can you avoid having a border? You can’t have an open border any more, you have to have a border where people are checked as they go from Scotland into England.”
Ms Sturgeon will this week set out plans to target “soft” No voters from 2014 in a fresh independence drive.
But the delay in launching the campaign came under fire from Mr Brown who said the SNP should have been “putting their arguments now so the public can test them.”
The First Minister has warned that another vote on Scotland leaving the UK is “highly likely” in the aftermath of the Brexit vote as she seeks to retain the country’s relations with the EU.
Nationalist backbench MSP James Dornan said: “The very real threat of Scotland being dragged out of the EU against our will is causing people to fundamentally rethink firmly held views on the constitution.
“Gordon Brown was behind Labour’s decision to block the transfer of employment protections, of more revenues and of greater responsibility to the parliament, so this conversion is very welcome.”