East Midlands Ambulance Service chief executive Phil Milligan is leaving the organisation after nearly two years.
John Sargeant, director of finance and performance will take his place until a successor is appointed.
News of his exit comes just weeks after EMAS was fined £3.5m after it missed its national targets for patients involved in life threatening emergencies for the third successive year.
The target is to get 95 per cent of cases within 19 minutes, but EMAS only achieved 91.85 per cent.
Under Mr Milligan’s leadership, EMAS approved plans to replace 65 ambulance stations with nine super hubs, 19 stations and more than 100 community points.