Whistles chief executive Jane Shepherdson has left the business after eight years in the role.
The business will now be led by brand director Helen Williamson, managing director Justin Hampshire and creative director Nick Passmore.
Shepherdson has already signed off the brand’s autumn 2017 collections.
She will now focus on her charity projects, as well as travelling.
In March, Phase Eight owner The Foschini Group acquired a substantial majority shareholding in Whistles for an undisclosed sum.
In April, Whistles appointed Phase Eight’s chief executive Ben Barnett and chief operating officer Lee Harlow to the board.
Shepherdson said: “I am really proud of what we have achieved at Whistles and am confident that I am handing over to a strong team in Helen, Justin and Nick, to continue the development of the brand.”
Barnett, who is chairman of Whistles, added: “We would like to thank Jane for her outstanding contribution to the rebuilding of the Whistles brand. She has established a clear direction for the future development of the brand and in Helen, Justin and Nick we are privileged to have an exceptional management team to realise this vision.”