Swiss group Richemont has made a bid approach for the luxury clothes online retailer Net-a-Porter, British newspapers said Sunday. The deal would make the company worth up to 350 million pounds (530 million dollars, 385 million euros), The Sunday Times and The Sunday Telegraph reported. Geneva-based Richemont, which is home to leading brands including Cartier and Alfred Dunhill, already controls a 29 percent stake in Net-a-Porter.