The management shuffle was sparked by Reitzle's decision to join Linde, the German engineering and industrial gases group, as chief executive. He is understood to have been unhappy at Ford following the removal last year of then chief executive Jac Nasser.
Nasser created the role at PAG specifically for Reitzle, who will retain a consultancy role at Ford. Fields will assume the PAG role in July.
Ford has also announced that management control of its Lincoln brand would transfer back to North America, leaving PAG with the European brands Land Rover, Jaguar, Volvo and Aston Martin.
Bill Ford, chairman and chief executive officer, said: 'We are committed to the Premier Automotive Group strategy. These brands are strong and that strength stems from exceptional products and talented people.'