"We can't give our children a one way ticket to an uncertain destination," warned Alistair Darling at the launch of Better Together, the campaign to keep Scotland as a partner in the UK.
The former chancellor argued that pro-unionists must "make a positive case for staying together".
But SNP MP Angus MacNeil told Total Politics that the Labour MP had made his case through "fear and worry".
"Our children only live once," he said. "We've got to make the right decision for them."
Speaking alongside MSP Annabel Goldie, Alistair Darling told an audience this morning: "This referendum challenges all of us in Scotland to answer some deep questions – not just what we believe but who we are.
"We are part of a social union underpinned by an economic and political union.
"We need more growth, more jobs for a new prosperous Scotland.
"The choice we make will be irrevocable.
"We can't give our children a one-way ticket to a deeply uncertain destination."
He criticised calls for independence as "a gamble", adding: "The SNP don't know what independence will mean for Scotland.
"What is a justification for such upheaval? Why would we want to turn our biggest market into our biggest competitor?"
And the Scottish MP tried to move the campaign beyond party lines, stating: "Even if you've never joined a political party before, it doesn't matter. Come and join our cause."
But fellow Scottish MP, Angus MacNeil, hit out at Darling, describing his speech as "riddled with inaccuracies".
The SNP politician said that England is now a bigger market for Ireland than it had been before, and unemployment in the UK is now higher than it ever was in Iceland since the crash.
Business will not be affected by independence, he added.
"When businesses phone each other, they don't ask whether we share a government," MacNeil told TP.
He dismissed Darling's performance as "empty".
But added: "I think he read the teleprompter brilliantly."