Ed Miliband appealed to Scottish voters' desire for 'social justice' in his biggest intervention yet in the independence referendum campaign.
The Labour leader sought to win over undecided voters in the September 18th poll by arguing Alex Salmond and David Cameron would be forced into a "race to the bottom" if Scotland left the rest of the UK.
He told delegates at Scottish Labour's spring conference in Perth that 'powerful interests' would persuade the governments in London and Edinburgh to lower the highest rates of tax and cut wages and working conditions.
"If Scotland was to go independent, it would be a race to the bottom not just on tax rates, but on wage rates, on terms and conditions, on zero hours contracts, on taking on the energy companies, on reforming the banks," Miliband said.
"Those who can afford it will be paying less, while hardworking families across Scotland will pay more and see their services suffer.
"Alex Salmond who claims to be a great social democrat would end up running the same race to the bottom that the Tories have embarked upon.
"The SNP talk about social justice but they can't build it - because they can’t be narrow nationalists and serve social justice at the same time."
Miliband used his speech to lay out Labour's plans to advance social justice by taxing bankers' bonuses, restore the 50p rate for those earning over £150,000 a year and introducing an energy price freeze - a measure Salmond has not committed to.
But he also avoided the fact that it would be much harder for Labour to win an overall majority in a UK without Scotland because of the relative dominance of the Conservative party in England.
"The SNP want to tell you that there is a progressive Scotland and a Tory England," Miliband added.
"There isn't. There are millions of people across every part of our country who want a better future for all our young people; who say it is just wrong that so many people in work find themselves in poverty, who want to be part of a country that is more just, more equal, more fair."
Miliband invoked the memory of former Labour leader John Smith as he rallies the Labour party in Scotland behind the campaign for independence.
And he talked about his father's time in Scotland training with the Royal Navy during the Second World War.
"I passionately believe in Scotland staying in the United Kingdom," he said.
"It is a belief rooted in the history and bonds that we share together across this United Kingdom: a history that has enabled us to fight better for equality and social justice across this United Kingdom."