The Senior Alliance is offering free membership for the over-50s, and plans to fundraise for other charities but does not intend to register as a charity itself.
The alliance's follow-up letter says the alliance is raising funds for "research into a wide range of such causes including Alzheimer's disease, diabetes, arthritis, tinnitus, age-related cancers and better treatments for back pain".
Richard Trantom, the Alzheimer's Association's secretary and a founder of the Alzheimer's Foundation, which was wound up in 2002 after a Charity Commission investigation into its fundraising, told Third Sector the association had signed a deal with the alliance for a fundraising pilot "some time ago", but was not aware it had begun. He said the association had stopped fundraising during the investigation.
"Unbeknown to us, they had already started to fundraise," he said. "We've told them not to do anything at the moment."
Chris Stoddard, the alliance's honorary secretary, said a trial telephone appeal for the Alzheimer's Association in the Birmingham area had produced a 20 per cent positive response.
He said: "The beneficiaries of the alliance's fundraising will be decided by the membership after our formal launch in January." He said the alliance was a "not-for-profit membership pressure group" and would seek sponsorships.
However, Stephanie Smith, fundraising director at the Alzheimer's Society, which has complained to the Institute of Fundraising and the Charity Commission about the association, was surprised to learn of the Senior Alliance's existence. "We didn't know anything about a new membership organisation, and I am very surprised that it is working with the association, given that it is under investigation by the FSA."