The trust manages Singleton and Morriston hospitals in Swansea

But health officials say the efficiency programme will mean it will still treat the same number of patients by cutting down the time they spend in hospital.

Amicus and British Medical Association staff officials say the move is needed to safeguard services and patient care but Unison said it was "unacceptable".

The union called a mass meeting of its members on Tuesday afternoon.

It has called for a halt to the bed closure programme claiming it was being driven by "financial cut-backs and not any planned improvements in health care".

The trust, which currently employs 9,500 staff and manages health services across the city including Morriston and Singleton Hospitals, claims it could be �15.5m in debt by the end of this financial year.

Independent reports have made it clear that Swansea's hospitals have too many beds Calum Campbell, trust chief executive

It said it has been able to avoid large debts in recent years through �one off" savings but now needed to introduce a programme of clinical efficiencies.

It said around 750 posts would go over the next three years through "natural wastage" and there were no plans for redundancies.

It said it would reduce 86 beds from around 1,800 that are currently used.

In a letter to Unison acting trust chief executive Calum Campbell said: "Independent reports have made it clear that Swansea's hospitals have too many beds and we have been inefficient in the way we have managed care.

"Increasing our day case rates and reducing lengths of stay means patients are in hospital for shorter periods of time."

This can only be done when it is safe to do so Jeff Baker, Unison

But Unison's regional organiser Jeff Baker said the trust had failed to consult with staff.

He said those working in wards in orthopaedics and general surgery had been told they were being reduced to a Monday to Friday service.

"We realise that what may lay behind the proposals is . . . what may be the unnecessary use of acute hospital beds.

"However, this can only be done when it is safe to do so - when community services are in place and with alternative uses found for any unused beds."

A spokesperson for the Welsh Assembly Government said had been assured the cuts would not have an adverse effect on services or patient care.

"Assurances have also been given that the effect on staff can be absorbed through normal staff turnover and reduced use of agency cover," they added.