Consumers have accused Disneyland Paris of illegally blocking their access to cheap deals available to residents of France or Belgium. This is mostly achieved through residence-based payment and delivery rules, selective offers, or by redirecting consumers to more expensive prices on their national websites.
Elzbieta Bienkowska, the EU commissioner for the single market, said a spate of complaints "were very significant, particularly in one or two instances".
"It is time to get to the bottom of this," she said. "I am interested in answers and explanations. On the face of it, I struggle to see what objective justification there could be for these practices."
A spokesperson for BEUC, the European consumers' group, welcomed the Commission taking steps to enforce its rulebook and "clarify what constitutes an unjustified discrimination".
"Geoblocking can lead to price discrimination, is against single market principles and restricts consumer choice," the spokesperson said.
The initial findings found British consumers paying around 15 per cent more for one-day tickets, according to the preliminary EU assessment. French consumers also benefit from other perks, including large family discounts, special rates, annual packages, monthly payment options and offers to buy tickets at one Disneyland park rather than two.
Under EU rules prices can be varied according to nationality if there are objective reasons, such as different market conditions, seasonal fluctuations in demand or different holiday periods. Disneyland Paris says that its promotions in local markets are based on booking patterns and school holidays.
However a Commission "sweep" of Disneyland Paris' rivals in Europe — including Denmark's Legoland and Tivoli Gardens and Germany's Europapark — found that other operators did not vary prices to the same extent.
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Ms Bienkowska's assault on price discrimination is part of a broader Commission push to eradicate so-called geo-blocking in Europe, where consumer IP addresses or payment cards are used to bar them from certain services.
A separate Commission competition case, launched last week, accused top Hollywood studios and Sky UK of entering illegal agreements to stop EU consumers from accessing pay-TV services available in the UK and Ireland. All the companies are contesting the charges.
If no action is taken by France against Disneyland, the Commission can ultimately take France to court. When faced with similar regulatory objections last year, car rental companies in Europe agreed to stop rerouting consumers to their national websites.
Critics of the "price discrimination" clampdown argue the practice is a legitimate pricing model that allows companies to be responsive to differences in local markets in Europe and avoid one-size-fits all prices.
Disneyland Paris defended its pricing policy, saying it ran well-justified discounts and promotions in local markets. "When purchased directly with Disneyland Paris, the cost of a basic resort package — without promotional offers — is identical across all markets, give or take exchange rates," the company said.
"Throughout the year we try to attract guests from different markets by offering market-specific 'book-by' promotions that can include discounts. Those promotions take into consideration factors specific to people in the local market, such as their school holiday calendar and booking patterns."
It added that consumers can contact the central reservations office if they see a promotion outside their local market "and request to make that specific booking".