Bill Howatson sent an e-mail to NHS Grampian staff yesterday expressing his “deep regret” over his resignation.
In a letter designed to take the sting out of the government announcement later in the day, the former provost of Aberdeenshire said: “This has been a very difficult decision to take.”
He paid tribute to the health board as an “outstanding organisation” and to the staff who made it so.
Mr Howatson, who is Aberdeenshire councillor for the Mearns, said major “visible” achievements had been the teaching and medical training complex – the Matthew Hay Building – the Aberdeen Health and Care Village, and primary care facilities in Forres.
He also cited the redesigned maternity service and services for children with complex needs as successes and praised the “care and compassion shown to patients”.
Mr Howatson added: “However, it has become clear during the course of this year that we face significant challenges. I am aware of these and of the concerns that have been expressed.
“Despite our very best efforts and the tireless commitment of many of you we still have more to do to meet waiting time targets in a sustainable way.
“Developing and maintaining sustainable staffing in areas such as the emergency department has been difficult and many of you feel under considerable pressure.”
Mr Howatson said these issues and others were being addressed.
He added: “I have reluctantly decided that to give the best possible chance of success to future endeavours the board should move forward under new chairmanship.
“I urge you all to unite behind the board, the chief executive and the senior team.”