Mahesh Patel, the group managing director of Manchester-based clothing supplier SRG Apparel, will leave the business in January.
Patel has worked for companies owned by the Passi family, which include By Design PLC , SRG Apparel and Missguided, since 1992.
He is setting up his own firm as a business consultant in 2017.
Patel joined SRG Apparel in 1999 as director and was promoted to group managing director in 2013. His replacement at the firm has not yet been appointed.
He has also served as a director at Missguided since it was founded in January 2009.
Patel said: “I am coming to a stage in my life that it’s now or never to fulfil a personal ambition of mine to work for myself as a business consultant. I will take away only wonderful memories of working for the family and will always wish them success in their various business ventures.”