Yes Scotland no longer fully reflects the wider groups of people and parties seeking independence, Green party member Stan Blackley said.
“The wider Yes campaign has become a movement of the people, become cross-party and non-party with those without party affiliation now vastly outnumbering those with it,” he wrote in the Sunday Herald newspaper.
“It has moved away from political identities to become something more diverse and more convincing than the SNP, and in doing so has left Yes Scotland behind. In many ways, the Yes Scotland organisation is now redundant.
“In my opinion, this is just as well, as that organisation has become little more than an SNP front in recent months, which is ironic given the amount of effort that was put into fighting that perception in the early days.”
Mr Blackley was deputy director of communities at the group from September 2012 until January this year. He was already established as a vocal campaigner with groups such as Friends of the Earth Scotland.
His comments were seized upon by critics who claim non-SNP members of Yes Scotland, such as Green leader Patrick Harvie and former Labour politician Denis Canavan, have been deceived.
Scottish Labour deputy leader Anas Sarwar said: “While Alex Salmond argues that a vote to break up Britain isn’t a vote for the SNP, Stan Blackley’s admission blows that argument apart. The campaign to take us out of the United Kingdom is run by the SNP, funded by the SNP and is the SNP. Put simply, it’s Yes for Alex Salmond.
“Denis Canavan, Patrick Harvie and others have been deceived. They are simply there to add a veneer of variety to Salmond’s campaign. But Scots will see through their attempt to pretend to be something they aren’t. If they had a shred of honesty and self-respect, they would refuse to allow themselves to be Alex Salmond’s stooges.”
The Greens set up their own distinct group to campaign for a “yes” vote while reflecting their policies.
Mr Blackley claimed the Yes Scotland organisation was “dysfunctional” from the start.
“I survived 16 months working at Yes Scotland, during which time I witnessed more roaring tantrums, faux resignations, bad-tempered walk-outs, pointless meetings, chaotic activities and last-minute panics than in the rest of my 25 working years put together,” he said.
Green co-leader Patrick Harvie said: “The Yes campaign is about far more than the personality politics in the Hope Street HQ.
“It’s a vibrant grassroots movement, supported by Yes Scotland, which is clearly building great momentum, and I believe the Green Yes campaign is making a significant contribution to that success.”
A Yes Scotland spokesman said: “Stan Blackley was dismissed by Yes Scotland in January as part of a change of initiative in the grassroots area of the campaign, which we believe is key to achieving a Yes vote in September. We are grateful to him for the contribution he made while he was employed at Yes Scotland.
“The momentum is now clearly with the Yes movement and whatever personal issues he has, we are sure Stan will wish to play his part in securing a Yes majority in September.”