The new chairman of a mental health trust said his organisation remained committed to the radical redesign of services in Norfolk and Suffolk, despite the resignation of its chief executive.

Unions and campaigners against the reduction of front-line staff and inpatient beds at Norfolk and Suffolk NHS Foundation Trust have called on officials to rethink their plans following the news that Aidan Thomas was standing down after four years in charge.

However, Gary Page, who became chairman of the NHS trust in April, said managers and directors were ploughing on with a strategy to reduce 500 jobs and cut 20pc of inpatient beds as part of a strategy to save money over the next four years.

He said: 'The trust board and service strategy lead clinicians remain 100pc committed to implementing the trust service strategy, on which we have consulted widely. The strategy implementation has already comm-enced and will continue in line with the previously published timetable.

'I strongly believe that this redesign of services is essential for the trust and our service users across Norfolk and Suffolk and will lead to improved services in a number of areas,' he said.

Mr Thomas announced his resignation last week after admitting that he had been considering his future following the merger of Norfolk and Suffolk mental health trusts in 2011. He added that he had been struggling with the regular commute from his Essex home and said his style of management was better suited to a smaller organisation.

Deputy chief executive and finance director Andrew Hopkins will take over as acting CEO from July 1, amid concerns about the trust's plans to reduce its budget by 20pc by 2016.

Mr Page, who became chairman following the retirement of Maggie Wheeler, added: 'Andrew is the best person to continue with implementing the strategy changes. Andrew was instrumental in the development of the strategy throughout 2012 and his experience will be invaluable going forward.'

The proposals of Norfolk and Suffolk NHS Foundation Trust to cut 502 out of 2,128 posts and have 86 fewer inpatient beds is based on developing a new single access and assessment service across the two counties and having more care in the community.

However, concerns have been raised by commissioners about the pace of change and the Clinical Commissioning Groups in Norfolk and Waveney have pledged £1.3m in transitional funds as the changes take place and another £300,000 to fund dementia assessment beds at the Chase Ward in west Norfolk.

Dr Rob Harwood, chairman of the Eastern regional consultants committee of the British Medical Association, said they were sorry to see Mr Thomas go.

'The appointment of a new chief executive provides an opportunity to rethink the inadvisable cuts to staff numbers that are planned at the trust. This is a time of massive disruption and upheaval, and staff are increasingly concerned about the safety and quality of services.

'Quite simply, we worry that the planned cuts mean there will not be enough front-line staff to continue to provide the current range of high-quality, safe services,' he said.

Emma Corlett, communications officer for the Norfolk and Suffolk NHS Foundation Trust Unison branch, added: 'Aidan's resignation comes at a time of enormous upheaval and uncertainty for our members, and for people who rely on the services that we provide.

'The precarious financial state that NSFT finds itself in is the result of what happens when services are commissioned with savage cuts. No one wants to manage a sinking ship in the absence of any life rafts. We desperately need the new clinical commissioning groups to provide life rafts in the form of funding to protect services and local jobs.'

Forty-one mental health workers at the Julian Hospital in Norwich and Chatterton House and the Fermoy Unit in King's Lynn were told earlier this year they were being made redundant as part the restructure involving Dementia and Complexity in Later Life services.

Norfolk and Suffolk NHS Foundation Trust has also announced it is looking at reducing beds at Carlton Court Hospital in Carlton Colville, near Lowestoft, and replacing them with dementia intensive support teams to provide care for more elderly people at their homes in the Waveney and Yarmouth areas.

Bob Blizzard, prospective parliamentary candidate for Waveney, who has been campaigning against the loss of beds at Carlton Court, added: 'With the sudden resignation, not long after they have a new chairman, I hope this may lead to some sort of rethink. Carlton Court was only open six years ago and it would be an incredible waste to close a new NHS facility.

'Things are going wrong in this trust and I would urge them to think again,' he said.