The Chancellor, Mr Gordon Brown, has launched a new Labour offensive against the Scottish National Party, warning businessmen that Scotland could not afford the cost of separation from England.
Given the interdependence of Scotland's trade with England, and with 28 of the country's top companies English-based, "Scotland simply cannot afford the job losses that would come from SNP policies, or afford the SNP chasing companies away," Mr Brown told the Institute of Directors conference in Perthshire yesterday.
The Chancellor's speech marked the beginning of a planned week-long Labour attack on the SNP's "separatist" policies. With the legislation creating the Scottish parliament soon to clear Westminster, Mr Tony Blair's high-profile visit next week will mark a further intensification of a bitter political battle likely to continue to the elections next May.
Mr Brown said the new parliament would give Scotland a large measure of control over issues like unemployment, education, health and help for small businesses. And with the advent of devolution it could no longer be claimed that Scotland's nationhood or civic institutions were at risk.
"It is now for those advocating the case for separation to explain why they would move from devolution to separation," said Mr Brown. "Explain what possible gain from imposing costly new barriers by abandoning everything and anything British - and to explain why they want to see the country on a path of constitutional confusion and confrontation for many years to come."
The scale of convergence between the two countries meant that Scottish personal disposable incomes now stood at 99.5 per cent of English levels. And the degree of interdependence was such that most of Scotland's trade was with England, while 50 per cent of its exports were to the rest of Britain.
"In almost every area," said Mr Brown, "England is our biggest customer." He went on: "To an extent far greater than any separatist realises or would care to admit, Scotland's economic future is bound with the rest of Britain, and any instability in the trading relationship between Scotland and the rest of Britain could have an enormous impact on Scottish businesses and Scottish jobs."
He challenged nationalists to say why they wanted to impose "new and costly barriers" between Scotland and the rest of the United Kingdom, costs he claimed could run into "billions" in setting up financial transactions based on different currencies, and big costs for the corporate sector which would follow separation.
"These cannot be dismissed as a matter of minor inconvenience because these would increase costs substantially for every business in the country," said the Chancellor.
Later the SNP mocked Mr Brown's attack, calling it "absurd and desperate". The party's treasury spokesman, Mr John Swinney, said: "All that Gordon Brown is doing is recycling the same discredited argument.
"His argument is economic gibberish. The only job threatened by the process of independence is Gordon Brown's. It obviously isn't necessary to be in the same state to trade with other nations."