Leading Japanese casual wear giant and owner of the hit Unqilo fashion label, Fast Retailing Co Ltd, on Friday posted a 39.9 per cent plunge in July same-store sales - its tenth consecutive monthly sales fall.

The company said in a statement customer visits slumped 33.5 per cent in July from the year-ago period in the wake of a 29.4 per cent fall in June, with per-customer spending down 9.6 per cent last month.

The chain said sales of T-shirts and shorts made from quick-drying breathable materials sold well last month and the slump in same-store sales was not as steep as the 44.2 per cent drop reported in May.

It added for the 11 months through July, same-store sales fell 28.6 per cent from a year prior while total sales fell 16.7 per cent.

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.