The Indonesian association of synthetic fibre producers has blamed cheap imports for a 35 per cent slump in the country's yarn and synthetic fibre sales.

Association chairman Asima N Sitorus said normally sales increase by 30 per cent-40 per cent toward the peak end of year season, pushed up by growing demand.

He said October sales of synthetic fibres and yarns came to 24,000 tons, less than half the 50,690 tons sold in the same month last year - and predicts December sales will fall even further.