The items should be at most 20 per cent higher than food sold at leading department stores,” General Viddhavat Rajatanun, one of the three ombudsmen, said yesterday.

Airports of Thailand (AOT) and the Internal Trade Department must take action against airport shops that refuse to obey the rules, he said.

Inspections around Don Mueang Airport have found that food and beverages there are 40-200 per cent more expensive.

The Ombudsman investigated the matter after receiving complaints from the public.

AOT has been instructed to check food and beverage prices at leading department stores, together with the Internal Trade Department, and issue standard reference prices within 30 days.

Some Don Mueang merchants claimed that they had higher expenses, so they had to charge more.

“Our staff, for example, must be fluent in foreign languages like Mandarin and English. And consumers have plenty of choices. Some shops here in fact charge just Bt5 more per dish than restaurants outside,” an airport shop owner said.