Tony Blair has launched a savage attack on the "outdated, reactionary" views of the Scottish National Party (SNP), saying it cannot provide Scotland with hope.
In a speech to the Scottish Labour party conference in Oban, the prime minister said the question of whether Scotland should be independent was an "old debate" such as EU withdrawal that had "long since lost its relevance or its sense".
"But it is a grievance which, if indulged, has a consequence. The reason I detest this narrow nationalism is not because it engenders fear but because it squanders hope," he said.
However, SNP leader Alex Salmond said the "hysteria" of Mr Blair's attack was a tribute to his party's success in "pinning Labour in Scotland on the political ropes".
He cited yesterday's YouGov poll showing the party was on course to meet its target of 20 constituency seats in May's Holyrood elections. Thirty-six per cent of voters said they would vote for the SNP in their constituency, compared to just 29 per cent for Labour.
"His attacks reinforce our position as the only challengers to Labour next year, and undermine any pretence that Labour in Scotland are capable of standing on their own two feet without interference from London," Mr Salmond said.
"These desperate attacks are not a substitute for the substance Labour are clearly lacking, and are just another reason why more and more Scots believe that it's time for a change in Scotland, and time for the SNP."
However, Mr Blair accused the nationalists of trying to be "all things to all people" in their efforts to prove they were different from Labour but ended up having nothing but the "politics of grievance".
"Their argument has departed but their obsession remains. And it is sad because whereas we should be debating the virtues of this or that policy, issue or personality, we are forced to debate again a cause - the union or separation," he said.
Mr Blair condemned the SNP's economic policy, saying it relied on Scotland taking control of its oil reserves and attempted to predict the price of this resource in the future - something that even the best experts found hard to do.
But he said the worst thing about a possible nationalist win next year would be "what it says about us, about the people, about our nations - that at a time of momentous challenge when our path to progress was clear, we lost our nerve and turned in on ourselves".
However, Mr Salmond replied: "This is a replay of previous Labour attempts to 'engender fear' in the SNP. It's simply 'cauld kale het up' [yesterday's leftovers] by a desperate, discredited man."