Sir John Banham, a trustee of the charity ShelterBox, has resigned after the sacking of Tom Henderson, its founder and chief executive.
The charity, which provides survival equipment to people affected by disasters, earlier this week said it had removed Henderson as chief executive following a unanimous decision by trustees.
But Banham, a former director general of the Confederation of British Industry and the first controller of the Audit Commission, said he had not agreed to Henderson’s sacking and has stood down from the board.
The charity declined to disclose the reasons behind Henderson’s removal and said Henderson was offered a job as president of the charity, which he declined.
But Banham told Third Sector this was not the case.
"I was not present when the decision was taken [to sack Henderson] and I resigned when the offer of the charity’s presidency, a pivotal role which I helped design and which Mr Henderson had accepted, was withdrawn," he said.
"The question of Mr Henderson’s dismissal was never discussed by the board, to my knowledge, and I never agreed that he should be dismissed.
"I have never been anything other than hugely supportive of the charity and I have made no allegations about it," he added. "It’s a wonderful charity that does terrific work around the world and the sooner it’s back on track the better."
A spokeswoman for the charity said it would not retract its earlier statement that the decision to sack Henderson was unanimous.
She said she was unable to comment fully because the charity did not wish to prejudice any ongoing processes. Henderson is appealing against the decision to remove him as chief executive.
The spokeswoman said: "ShelterBox is saddened that a former trustee has made allegations about the charity.
"In the interests of the charity, it must confirm that the charity’s board of trustees followed sound legal advice throughout this matter."
Third Sector was unable to contact Henderson, who received an OBE in 2010 for services to humanitarian aid.