British Boxing Board of Control doctor Dr George O'Neill has quit following the decision to give Wayne McCullough a licence to box in Britain.
Belfast doctor O'Neill's decision was followed by the resignations of three other doctors who are connected to the Northern Ireland area council for the board.
A cyst was found near McCullough's brain two years ago when he was set to box in Belfast and that led the board to refuse him permission to fight.
But last week the board decided to give McCullough a licence to box and he is expected to make his return to a British ring on August 17th in Cardiff.
O'Neill said: "I feel that ethically and morally I can no longer be part of boxing.
"I will not discuss individual cases but my views are quite clear.
"I have been working 20 years with the council and I will miss boxing. I have made many friends in the sport.
"It is unfortunate that I have had to make this decision but I feel I have no alternative."
Northern Ireland area council secretary John Campbell added: "I can understand why George has done this. It is on a matter of principle but I wish that he would reconsider.
"George has brought a lot of safety to boxing and we can't afford to lose people of his stature. I wish he would stay on to help the boxers."
PA