London Heathrow has slammed a report from online price comparison site Kelkoo, which found that the British airport offered the worst tax-free prices in Europe.

The airport described the Kelkoo report, released August 16, as "misleading and incorrect", saying that it included products that the airport does not sell.

In its report, Kelkoo claimed that tax free goods in European airports were 6.2 percent cheaper on average, but the discount at Heathrow was only 3.1 percent, the worst of any major European airport.

French airports, led by Lyon St Exupery and Paris Charles de Gaulle, offered the highest tax-free savings at 11.9 percent and 11.5 percent respectively, said Kelkoo.

In its mystery shopping exercise, the site looked at 22 products across a variety of categories and locations and compared them to the recommended retail price in high street stores.

It discovered that an Apple iPad could cost anything from £556 (€668) in Rome to £579 (€706) in the UK, while in contrast, Estee Lauder Advanced Night repair is just £46 (€56) at London's Gatwick, but almost double in France at £90 (€110).

It concluded that while Europe's airport "tax free" outlets offer savings against the high street prices in some categories, online discounts were consistently higher.

Heathrow, which is the second largest duty free market in the world, said that it was "perplexed", adding that the data used by Kelkoo was based on inaccurate prices.

"All passengers, travelling from Heathrow, regardless of destination, are offered a single price enabling them to take advantage of great savings across a wide range of products and brands compared to the high street, typically at discounts of 15% or more," said the airport in a statement.

Discounts offered by Europe's airports against the high street price
Data from Kelkoo

1. Lyon (-11.9%)
2. Paris (-11.5%)
3. Schiphol (-6.1%)
4. Frankfurt (-5.6%)
5. Gatwick (-5%)
6. Barcelona (-5%)
7. Madrid (-4.7%)
8. Rome (-4.7%)
9. Berlin (-4.6%)
10. Heathrow (-3.10%)