Packaging firm British Polythene Industries (BPI) has warned of a buffeting from market conditions that could hit profits.
The Greenock-based company said the increased volatility of input prices is causing problems.
It claimed that many suppliers scaled back production, keeping stocks down, and took advantage of disruption to petro-chemical refineries in France.
BPI said it continued to be hit by polymer price increases.
News that profits could be lower than expected sent shares down 5%.
"It is difficult to be certain about input costs for November and December, and our current profit expectations for the full year before property gains, restructuring costs and pension financing, are towards the lower end of current market forecasts," according to a statement to the London Stock Exchange.
BPI said it still expects profits to be well ahead of last year, helped by cost reduction and a move of production from its Brampton factory to more efficient sites.
BPI employ 350 of its 2300 workers at plants in Scotland and provides packaging for a wide range of industries.