A volunteer who was dismissed from Lincoln Citizens Advice Bureau after she complained about her manager fears that the investigation the charity has launched into the affair will be a "whitewash".
Lettie Fortune was told not to return to the bureau after writing to Tom James, its chair, to allege that she and others had been treated unacceptably. James claimed the letter was defamatory.
Citizens Advice, the national body for local bureaux, put pressure on Lincoln CAB to launch an inquiry.
A Third Sector article highlighted the story earlier this year.
But Fortune is concerned that the investigator, David Chiddick, the vice-chancellor of Lincoln University, was appointed by the trustees of Lincoln CAB rather than by the national body.
She said Chiddick had been asked to investigate James's conduct but not to examine her original complaint. "The two are inextricably linked," Fortune said. "The substantive issues are as important as the procedural ones."
Fortune said she had no reason to doubt Chiddick's integrity, but reserved the right to appeal to the national body if the outcome of the appeal was not "fair".
"I have become very cynical and I think there will be a whitewash," she said. "It is dragging on and it is affecting my health."
A spokeswoman for Citizens Advice said: "Any complaint is taken very seriously to ensure it is treated fairly and investigated appropriately."