Several members of a local branch of the Alzheimer's Society have broken away and formed a rival group.
The former members said they had founded Action on Dementia Sunderland because the London-based society had become too centralised and unresponsive to local needs.
The society embarked on a major restructuring in November to win more public service contracts and improve accountability.
A total of 240 branches are being merged and placed under the control of 49 ‘localities', or regional administrative centres. Other branches have complained about the move but it is not clear whether they intend to follow Sunderland's example and break away.
"The Alzheimer's Society has become like a top-down quango," said Ernie Thompson, a founder member of the Sunderland branch of the society in 1987. He has relinquished his chairmanship of the branch to assume the same role at the new group.
"Local members have been totally sidelined," he said. "More and more charities are behaving this way. While everybody else is talking about more local control and accountability, big charities seem to be going in the opposite direction and becoming more centralised."
The Sunderland branch, which is being merged with other branches in the north-east, contributes about £400,000 to the charity's £45m annual income. The former members claimed they had not been properly consulted and were worried that the branch's building, paid for by donations by Sunderland people, could be sold and the funds swallowed up by the national body.
Ruth Sutherland, chief operating officer at the society, said the Sunderland branch was still operating but change was inevitable.
"The society has grown 70 per cent in the past five years and this unprecedented growth means we need to make changes to ensure we're equipped to meet the challenge that faces us," she said.
Sutherland said the charity had consulted from March to November last year. "We have no volunteering infrastructure despite being 30 years old," she said. "People like Ernie are used to complete autonomy and it's difficult for them to understand accountability."
Sutherland said she had received eight letters from people dissatisfied by the changes.
"I'm concerned because we want our volunteers to come with us," she said. "But the days of people not being accountable for public money have gone. There has to be a structure that shows we meet statutory regulators and can account for all our money."
She said there were no plans for the sale of the Sunderland building, but concerns about access for disabled people meant some services there might have to end.