Edward McCabe is stepping down as Hartwell plc's group managing director to head up the Jameel Group's software and e-business company, Ebbon-Dacs.
He will leave Hartwell, placed sixth in the AM100, at the end of the company's financial year, November 30, but will remain on the board as a non-executive director.
From December 1, Dees Caddick, operations director of Hartwell's motor division, will report to company chairman Samir Hamadeh.
Mr McCabe: "The Jameel Group set up Ebbon-Dacs earlier this year to provide web-based software solutions for the automotive and other retail sectors.
"The new technologies in the marketplace give the motor trade huge opportunities to be more effective at the front end of the business and much more cost efficient at the back end.
"Our first product, Leaselink, connecting contract hire companies and dealers, is already in the marketplace and this month we will be launching another, Integrated Showroom, which will provide the first fully integrated clicks and bricks solution for the retail motor trade.
"I have very much enjoyed my time as group managing director at Hartwell and I am glad my new role will keep me heavily involved in the sector."