Britain's government has urged shops at airports to lower the prices of tax-free items as a campaign for passengers to refuse to show their boarding cards over the issue gathered pace.
Sales tax, which currently stands at 20 percent, is not applied by the government to items sold in airport shops to people travelling to destinations outside the European Union.
Retailers are supposed to discount goods accordingly. But The Independent newspaper revealed this week that some stores were failing to apply the reduction, instead pocketing the difference.
Although this practice is not illegal, several British newspapers are urging passengers not to show their boarding cards, which reveal their destination, at airport shops in symbolic protest.
Treasury Minister David Gauke said: "The VAT relief at airports is intended to reduce prices for travellers not as a windfall gain for shops.
"While many retailers do pass this saving on to customers, it is disappointing that some are choosing not to.
"We urge all airside retailers to use this relief for the benefit of their customers."
At the height of Britain's summer holiday season, The Independent devoted several pages to the issue on Wednesday (local time), while the Daily Mail ran a story headlined: "How you can beat the great airport shop VAT rip-off – refuse to show your boarding pass!"