Net-a-Porter's listed status cramped Natalie Massenet's style

The Net-a-Porter founder Natalie Massenet decided to quit the online fashion retailer during a “summer of reflection” that included a spectacular 50th birthday party on the Italian coast, friends have said.

The former journalist shocked the fashion world on Wednesday night by walking away from the business she set up 15 years ago – weeks before the completion of a £1bn merger with its Italian e-commerce competitor Yoox.

Ms Massenet, who has made £100m from selling Net-a-Porter shares, is expected to launch a new company over the next few months, although it is unlikely to be a direct rival. Sources close to her said she had decided on holiday that she was “an entrepreneur at heart” and did not relish all the extra corporate obligations that come with leading a company quoted on the stock market.

She had been lined up to be executive chairman of the merged group when the proposed deal with Yoox was unveiled in March.

The decision to resign is believed to have been taken around the time of her birthday celebration in July. Dubbed Nat-a-Party, it was held in Positano on the Amalfi coast at the exclusive restaurant Da Adolfo, which was renamed Da Natalie for the day.

In a statement she said: “As for my own future, my entrepreneurial drive is as strong today as it always has been, and my passion for innovation will continue to be my greatest guide in business. The incredible experiences and memories of the past decade and a half, and the people I have had the honour to work alongside, will always be an inspiration to me.”

Friends played down reports of a bust-up with the Yoox boss Federico Marchetti and said the decision was driven more by her reluctance to embrace a role in a big, listed company.

Ms Massenet is the Californian-born daughter of a British Chanel model. She set up Net-a-Porter with her then husband Arnaud while she was pregnant with her first child, just as the dotcom crash hit in 2000 and amid warnings that women would not buy expensive clothes without trying them on. In 2010, she sold a stake to the Swiss luxury brands giant Richemont, making £50m.