The search has begun for the East of England Ambulance Service's third chairman in the space of a year following the resignation of Geoffrey Harris.

Dr Harris, who was announced as the interim chairman of the under-performing trust last May following the resignation of Maria Ball, said the time was right to stand down from the NHS trust after helping to bring in a new chief executive and non-executive board members.

The process for appointing a new chairman will be started immediately by the NHS Trust Development Authority (TDA).

Dr Harris' interim role at the ambulance trust was due to come to an end in May 2014.

He said: 'I have immensely enjoyed working at the ambulance service with such dedicated staff. I was asked to rebuild the trust board and leadership when I took on this interim role in May and I feel that having recruited a new non executive team and one of the most experienced ambulance chief executives [Anthony Marsh] in the country that it is the right time to bring in a new chairman. Over the last year the trust has made many improvements. There is lots more to be done but I am confident that under Anthony's stewardship the trust will continue to move forwards.'

Dr Harris has previously worked on NHS boards as chairman of NHS South of England Strategic Health Authority. He served as both chairman and deputy chairman of the General Optical Council from 2004 to 2010 and was also non-executive director and then chair of Buckinghamshire Mental Health NHS Trust from 2003 to 2006 and non-executive director of Stoke Mandeville Hospital NHS Trust from 1999 to 2003.

Anthony Marsh, CEO of the East of England Ambulance Service, said: 'It is with great sadness that I learnt of Geoff Harris' decision to stand down from his post as interim chairman and I wish him all the best for the future. Geoff joined the trust at the most challenging period of its history and has worked incredibly hard to both stabilise and reinvigorate the board, providing strong leadership and expertise to progress improvements.'

'We will be working with the NHS Trust Development Authority to start the process for appointing a new chairman immediately. In the meantime I am focussed on continuing to implement actions, such as the recruitment campaign for 400 new student paramedics we launched last week, which will directly improve our service and response to patients.'

Dale Bywater, director of delivery and development at the NHS Trust Development Authority added: 'It is with deep regret that we have accepted the resignation of Geoff Harris from his role as interim chairman of East of England Ambulance Service NHS Trust. Geoff's leadership has been critical in ensuring the ambulance trust now has in place the necessary foundations to tackle long-standing issues and improve services to patients. We would like to thank Geoff for his hard work in developing the trust board and his crucial support in setting them on the path to recovery.'