Exports orders slumped between 25 July and 15 August despite the Great Britain publicity drive that rolled into action during the Olympics.
Almost a third of manufacturers stated that overseas orders were below normal, according to the latest industrial trends survey by business CBI.
Total orders fell below the long-running average in August for the first time since December 2011. Output is expected to be flat over the next three months, following expectations of growth in the previous two surveys.
Only consumer goods companies predict a modest growth in production across the coming quarter, following a massive hit to sales over the past few months.
These output figures had strengthened in the previous two surveys but this unexpected weakness in export orders was broad-based, with a decline across the investment, intermediate and consumer goods sectors.
For the third month running, manufacturers do not expect to raise output prices over the next quarter. Only consumer goods firms indicated that prices would rise, albeit very modestly.