A top consultant at the Mater Hospital's Emergency Department has resigned, reigniting serious concerns over the unit's future, it can be revealed.
Dr John Gray, the clinical lead at the Mater Hospital Emergency Department, tendered his resignation by letter to the Belfast Trust before Christmas.
The Belfast Trust confirmed that it is currently advertising internally to replace the consultant's role.
Dr Gray, who had dedicated his career to the Mater, is set to leave in mid-March to work as a consultant at the Ulster Hospital A&E department for the South Eastern Trust.
It is understood the move will result in there being no full-time A&E consultant at the Mater. One part-time consultant along with locums will be employed.
A senior source at the Belfast Trust said Dr Gray had "worked tirelessly" to improve the A&E over almost a decade but had concerns over maintaining standards of care and safe levels of staffing.
"He was also frustrated at the lack of investment in the service as a whole," the source said.
"Most of the support services were being pulled away gradually. There are no paediatrics on site, or surgical cover, so they have to go to the RVH. He believed it was taking it away piece by piece."
Concerns have been voiced over the future of the Mater A&E department since November 13 last year.
Health bosses stopped children being treated at the hospital after concerns were raised over a lack of middle grade doctors and the impact on safety.
A decision was also taken to temporarily stop ambulances attending the ED from 6pm to 8am.
"I think they are trying to close the Mater A&E by stealth and I know that is what John feared. He tried his best but has had to admit defeat and walk away," the source said.
"After dedicating his career to the Belfast Mater he has to admit defeat and walk away which is very sad for the other consultants in the trust."
Last year Dr John Maxwell, clinical director of emergency medicine in Belfast, said senior doctors were being sought from Australia and across Europe to work in a Belfast emergency department as part of plans to solve the staffing crisis.
In a statement a spokeswoman for the Belfast Trust said: "Belfast Health and Social Care Trust is currently advertising internally to replace the Clinical Lead of the Emergency Department of the Mater Hospital.
"The closing date is 2pm on Friday, January 8, 2016.
"The Trust is continuously seeking to secure senior medical staff that will enhance the patient care service offered and is currently out to advert to recruit a number of doctors for the Emergency Departments in the Mater and Royal Victoria Hospitals."