Although official figures are not available until early April, they are expected to confirm the farmers announcement of a 43% reduction.
Prices have already risen sharply to reflect the reduced tonnage but importers are also facing additional costs due to the devaluation of sterling against the euro.
Production of extra virgin is down more than the crop shortfall due to poor quality "fallen fruit" - damaged prior to collection.
Italy is also down 12% and Greece is also lower than last season.
Total worldwide production is expected to be 2.25 million tonnes, with
demand at 2.6 million tonnes and rising.