The move follows the appointment of Jonathan Browning, 48, GM Europe vice president, sales, marketing and aftersales and the current chairman of Vauxhall Motor Limited as GM vice president, global sales, service and marketing.
Mr Parfitt (pictured) will also maintain his existing GME sales responsibility for GME Fleet and CV activities.
Mr Forster said: “Bill’s roles of chairman and managing director will provide strong continuity in the further development of GM’s UK operations and to continue to drive our business forward in the UK and Ireland.
“Bill has played a key role in leading the UK to become GM’s largest market in Europe and in building exemplary relations with our retailer networks.â€