Wine Intelligence's Paul Medder said: "The frequency of wine consumption among regular wine drinkers has started to settle out and the amount they drink is kind of reaching its natural ceiling."
The number of regular wine drinkers who say wine is important to their lifestyles or that they have a strong interest in wine has also dropped slightly since 2008.
Wine Intelligence also found a drop in consumer confidence and a rise in the number of people who believe wine is an expensive drink, from 22% in March 2008 to 35% in April 2011.
WSTA chief executive Jeremy Beadles, who chaired the LIWF debate at which the statistics were unveiled, said: "There is a significant risk of negativity when you see that data, with rising prices and lower consumer confidence.
"We are going to see the duty escalator of inflation plus 2% until at least 2014. There is going to be a pressure on increasing prices. Alcohol consumption has been dropping since 2004. There has been flat growth in wine and then slight declines last year in the on and off-trade.
"The reality is that volume is not where we should be focusing. Promotional activity which increased volume sales is declining.
"We have to look at a different shaped marketplace - really good businesses will make successful choices and make money."
Alison Levett, chief executive of Enotria, said the trade needs to find a new language with which to talk to consumers about wine, moving away from the technicalities of tasting notes it has used so far.
Moves to hand-sell sparkling wines as food accompaniments could get drinkers trading up and increase their average spend, according to Freixenet category development manager James Gray.
And Gonzalez Byass marketing director Jeremy Rockett said experiential, non-educational ways of teaching consumers about wine and its provenance could help boost average spend.