Leading Japanese casual wear giant, Fast Retailing Co Ltd, on Tuesday posted a 33 per cent plunge in June same-store sales compared to the year-ago period - its ninth consecutive fall in monthly sales.

The firm, best known for its value-priced Uniqlo chain, said that plunge was not as steep as its May same-store sales results which fell more than 44 per cent or its results for April when same-store sales fell more than over 42 per cent.

"Compared to last year, we have raised the number of products significantly and making a smooth transition," Fast Retailing said in a statement. "Also, customer numbers are recovering slightly."

Earlier this year, the company announced its founder and president, Tadashi Yanai, would step down as part of a management reshuffle but will remain as chairman.

Managing director Genichi Tamatsuka will take up the role of president in November.