Alistair Darling has ridiculed the idea of the UK retaining control of the Faslane nuclear submarine base even if Scotland became independent as "ludicrous".
The former Labour chancellor who heads up the cross-party Better Together pro-union campaign said he was "very glad when No.10 virtually disowned it" on Thursday morning.
"I think the idea is complete nonsense, it is misconstrued and misguided," he told HuffPost UK during a conference call with journalists on Thursday afternoon. "I was very glad when No. 10 virtually disowned it."
"It was clearly something that has emerged from someone in the MoD. The idea is just ludicrous and deserves to be put in bucket."
He added: "It's a stupid idea. And it won't make a blind bit of difference to the campaign."
Darling said had it been persisted with it could have had "some effect" on the referendum campaign and that it deserved to be "jumped on from a great height" as appears to have happend.
This morning The Guardian quoted an unnamed defence source as saying that the idea of a sovereign base would be "an option" to avoid the "eye-watering" cost of decommissioning the Faslane naval base on the Clyde, which would run into tens of billions of pounds.
However just hours later Downing Street moved to deny the story. A Number 10 spokesman said that no such idea had been presented to David Cameron or to defence secretary Philip Hammond, adding that it would not be a "credible or sensible" course of action.
The Downing Street spokesman said: "This government has not commissioned contingency plans over Faslane. No such ideas have come to the secretary of state or the prime minister. They would not support them if they did. It's not a credible or sensible idea."
Darling also criticised SNP leader Alex Salmond for waving the Saltire following Andy Murray's Wimbledon victory over the weekend.
"The only thing i saw was Alex Salmond standing up in the Royal Box with the Saltire. Like most normal Scots I went outside to enjoy the sunshine," he said.
"The sporting occasion spoke for itself, it was a sporting triumph it was nothing to do with politics. Frankly again the public take a dim view of when politician's try and muscle in on these things.
He added: "What we saw on Sunday was embarrassing."
Darling was speaking to reporters following a landmark speech on Scottish Independence in which he attempted to set out a "positive" view of the unionist argument.
"We're not just a part of an economic union, we are part of a social and cultural and a political union," he said. "Most of us living in Scotland are very proud to be Scottish, we are also proud to be British as well."
"For too long those of use who believed in the UK haven't put the case as clearly, consistently and as loudly as we should."