Luxury goods group Richemont has confirmed it will buy Net-a-Porter in a deal that values the online designer fashion retailer at £350m.

Founder Natalie Massenet will reinvest in the Net-a-Porter business alongside Richemont and will remain executive chairman.

Richemont already had a 28% stake in the business. It made an initial approach to buy the remaining shares in the business last month.

Richemont, which also owns the Chloe and Alfred Dunhill brands, imediately moved to reassure suppliers that Net-a-Porter would remain an independent business.

Richemont executive chairman Johann Rupert said: “At Richemont, we value the independence of our Maisons very highly. That principle will especially apply to Net-a-Porter as a platform for third parties. Becoming part of our group will provide the company with the support it requires to realise its business strategies.”

Net-a-Porter said that the Richemont investment would enable it to push ahead with its expansion plans over the next decade.

Net-a-Porter chief executive Mark Sebba said: “Initial trading for 2010 is continuing strongly with particular emphasis on an increase in first-time customers. We have extensive plans for the business over the coming years: apart from continuing to add new brands and enhancing the customer experience on the websites, we are making very significant investments into our infrastructure. We are moving our Headquarters into brand new offices at Westfield, in West London, and we are in the last stages of planning for substantial investment in automation and upgrading of our international Distribution Centre in South East London. In addition, this year will see us enlarging our New York based DC and we are exploring opportunities in South East Asia.”

Massenet added: “The business is continuing to grow, and its growth is well managed; consumers are embracing online shopping more than ever; technological breakthroughs and exciting innovation are giving us new compelling opportunities to interact with our customers and we are as motivated as ever to lead the way in the on-line fashion retail sector. We will be announcing exciting new plans for the business over the coming months.”

“Richemont has completely embraced our vision and strategy since they came on board as a shareholder and together we are going to continue to build the 21st century model for luxury fashion retailing. I am personally thrilled that so many of the team who were with us at the beginning will benefit from the hard work that put the company where it is today. I remain completely committed to this business and am enormously proud of and inspired by the talented and dedicated people who make up the DNA of the Net-a-Porter Group.”