Ardent Leisure boss Deborah Thomas will step down from the role she took two years ago, handing the reins of the troubled theme park and arcade operator to former Nine Entertainment chief operating officer Simon Kelly.

Ms Thomas, under whose watch the company suffered a fatal accident at its Dreamworld, Queensland, theme park in October and two months ago reported a weaker-than-expected performance at its US Main Event Entertainment business, will take on the roles of chief customer officer for the group and chief operating officer for its Australasian business on July 1. On the same day Mr Kelly becomes chief executive officer and managing director.