(ShareCast News) - Media distribution company MBL Group announced on Friday that Lisa Clarke is stepping down from her role as acting chief executive and finance director with immediate effect.The firm's board said Tim Jackson-Smith will become executive chairman on an interim basis."On behalf of the board, I would like to thank Lisa for the significant contribution she has made to the company over the last ten years and we wish her the best of luck in her future endeavours," Jackson-Smith commented.The company offered no further details on Clarke's departure.