Alistair Darling has written off the Scottish Government's formal prospectus for independence before it has even been published.
The Labour MP, who leads the formal Better Together campaign to keep Scotland in the union, said the White Paper setting out independence will be a "work of fiction."
Darling said that the referendum campaign is entering a crucial phase
"I'm looking forward to this White Paper coming out in a couple of weeks time because apparently it's going to have the answer to everything," he said.
"Whether it's welfare, the pound, the meaning of life, the whole thing.
"Scotland, among other things, has very many talented people and I think this is going to join the ranks as a remarkable work of fiction when it comes."
Speaking at the launch of Better Together's Glasgow branch, Mr Darling said that the referendum campaign is entering a crucial phase.
Joined at the launch by the Scottish leaders of the three main pro-union parties, Mr Darling warned supporters of the campaign not to become "complacent".
Mr Darling said: "With a year to go and the long-awaited White Paper just weeks away we are entering a crucial phase of the referendum campaign.
"We cannot afford to be complacent for one moment, we have a big fight ahead of us."
The former chancellor also argued that Scotland would struggle to have the same diplomatic clout in dealing with international crises like Syria if it chooses to leave the UK next year.
"Unfortunately and tragically, the atrocities that are being visited upon the people of Syria are going to continue," he said responding to a question about the controversial Commons vote against potential military action.
"Ultimately, the long term solution is going to have to be diplomatic and the UK has got far more clout in the United Nations, in the G20 which is meeting in Russia next week, than a smaller country ever would.
"I've been to lots of these meetings throughout the time I was a minister and large countries, particularly one with a reputation like ours, have clout.
"I don't think there's anyone in this room who wouldn't want to see the clout of the UK, if possible, along with other countries, trying to bring an end to the bloodshed taking place in Syria."