LONDON, United Kingdom — Another senior staffer has left Yoox Net-a-Porter Group SpA following the merger that created the online luxury retailer.

Naomi Hewitt, who was promoted to director of people and organisation in October, resigned in April, a company official confirmed Wednesday, declining to comment further. Hewitt quit for personal reasons, said a person familiar with the situation who asked not to be identified as they were not authorised to speak about it. She didn’t immediately respond to an e-mail sent to her via LinkedIn.

Hewitt's departure is a blow for Yoox Net-a-Porter chief Federico Marchetti, who had entrusted her with helping build a new corporate culture at the enlarged company, an effort seen by Citigroup analysts as key to the success of the business. Hewitt had been with Net-a-Porter since 2003, according to her LinkedIn profile. Net-a-Porter founder Natalie Massenet quit in September and a handful of other executives, including the managing director of the Mr. Porter men's site and the president of discounter The Outnet, followed shortly after.

Yoox last year merged with Cie. Financiere Richemont SA's Net-a-Porter in an all stock deal. YNAP, which has since added executives from Instagram and department store La Rinascente to its board and sold a stake to a Dubai property magnate, will lay out its five-year strategic plan next month.

By Andrew Roberts; editors: Matthew Boyle and Phil Serafino.