Potato Council revealed that, as the UK suffered one of the wettest Augusts in a century, total clearance up to 22 August was estimated at 16,700ha (12.8 per cent), compared with 18,900ha (14.5 per cent) in 2007.
Potato Council market analyst Rob Burrow said: "Rivers rose to nervous levels in many regions, particularly Herefordshire, with a risk of flooding from the Wye to adjoining potato fields. Crops in parts of Yorkshire were affected, with some suffering water-logging. Harvesting as a result of the wet (weather) has fallen behind last year when conditions were improving."
He said that, in the case of the crisping sector, some growers were called on to lift earlier than scheduled because other growers' crops had been rained off.
He added that very little lifting has been possible in Scotland - particularly in the worst-hit regions of East Lothian, Fife and Angus.
Northern Ireland was also affected by the downpours, receiving 75 per cent of the average August rainfall in just 12 hours on 17 August.
The wet conditions also caused blight to thrive - although Burrows said growers have got wise to the threat and are controlling it by shortening their spray intervals.
Tadcaster potato grower Adam Sykes told Grower: "Blight has been very bad because it breeds in these wet, humid conditions. Moisture is in the canopy so it's hard to hit the blight straight on (with spraying). You are going to get problems when considerable rain falls hours after blight spraying because (the spray) gets washed off."