LONDON • London's Heathrow Airport has apologised for a promotion at a duty-free store that required Chinese shoppers to spend a higher amount than other travellers to enjoy a special discount.

Chinese travellers were asked to spend a minimum of £1,000 (S$1,835) to receive a 20 per cent discount voucher for subsequent purchases, while other shoppers needed to spend only £250 to receive the same offer, reported BBC News.

The promotion was run by Heathrow Airport's commercial partner, World Duty Free.

The unfair policy sparked outrage on social media after a Chinese student who worked at the store posted about it on China's widely used microblog platform Weibo on Sunday.

The post has been viewed more than 10 million times.

The part-time sales assistant at Terminal 2 said he tried to get the voucher for a Chinese woman who had around £300 worth of Chanel products in her shopping basket, but the cashier told him that the woman needed to spend £1,000 because she was Chinese.

The store manager, according to news website Sixth Tone, later told him that the offer was indeed a "little bit unfair".

"I've been in England for seven years. This is the first time I've felt injustice and racism so deeply," wrote the student, who also referred to the store management as "white-skinned pigs".

Other travellers responded with their experiences, some vowing not to shop at the airport again.

@Julialoveksh wrote on Twitter: "Will never shop in the duty free store at Heathrow any more. Chinese customers deserve to be treated with respect!! What a hideous and discriminating event to happen in 2018!! Disgusting."

On Monday, World Duty Free - one of hundreds of independent retailers at Heathrow - issued a statement on Weibo, saying it had investigated and rectified the issue.

Heathrow Airport apologised on Weibo and Twitter, saying the retailer now "offers the same benefits for travellers to all destinations".

Chinese tourists are increasingly seen as big spenders across the world. Chinese travellers accounted for a quarter of Heathrow's duty-free sales in 2015, although they made up only 1 per cent of passengers that year, according to travel website Mafengwo's global travel shopping report.

During the Golden Week travel period in October last year, Chinese tourists spent £29 million in shopping districts across the United Kingdom.

The number of Chinese visitors to the UK increased by 33 per cent last year. They collectively spent £667 million, according to UK tourism authority VisitBritain.