A new ruling on buying tax-free abroad could mean more customers drinking at home.
The EU Court of Justice
ruling, due next week, is expected to allow people to pay duty rates from the
alcohol's country of origin.
This would mean customers could buy drink by mail order more cheaply than from on the UK mainland because the duty on alcohol here is among the highest in the EU.
The decision could ultimately lead to harmonisation of alcohol tax but some observers fear an influx of cheaper alcohol from abroad could mean new competition for pubs.
Wolverhampton & Dudley chief executive Ralph Findlay said: "Pricing between the on and the off-trade has been one of the
factors that has led to the switch to off-trade drinking. If this new move increases the differential, it's not going to make that any easier.
"It's going to make it more important for every operators to differentiate what they are doing."
Tadcaster managing director James Crawfurd-Porter agreed: "There are still people who want to go out and socialise and I don't think this will destroy us over night, but it will accelerate what we are already seeing."
British Beer & Pub Association spokesman Neil Williams said the expected ruling would hit the off-trade and the Treasury more, because people will still visit pubs for the experience.
The impact of the expected ruling emerged in advice from accountants Ernst & Young.
It follows the court's ruling in favour of people in Holland who protested against being charged duty by its Government on alcohol bought in France.