Heathrow staff whose duties include helping travellers to find their flights are paid commission to direct people to the airport’s shops, according to an undercover investigation.

The London hub’s website says that its “passenger ambassadors” are there to help people with their journey.

About 250 of them work on the airside of security at the airport but the Channel 4 programme Dispatches discovered that they have sales targets to meet, with those working at entry level positions expected to bring in about £2,500 a day.

They are expected to generate a total of £125 million of sales a year.

An undercover reporter who applied to become an ambassador claimed to have been given a different description of the job from that detailed on Heathrow’s website.

It reads: “The majority of the role will involve interacting with passengers, persuading them to shop if they had not planned to or encouraging them to spend more. ”

In one piece of footage an ambassador claims to average £10,000 worth of sales a day, or £1.6 million a year. Others said that they targeted Chinese passengers because they were likely to spend more than other nationalities.

Ambassadors helped Heathrow to achieve retail sales of £612 million last year.

Heathrow denied that it was misleading any travellers.

A spokesman said: “We provide fantastic restaurants and stores in order to offset the cost of running the airport, which ultimately keeps the cost of air fares down for passengers. Passenger ambassadors are an important part of our business and we expect the team to put the needs of our passengers first.”

The programme also examined prices and sales practices at World Duty Free, the chain of airport stores across the UK that has sales of nearly £1 billion a year.

It found that the shops stock exclusive deals, such as bigger bottles of perfume, which makes it harder to compare the price against high street outlets. It sells Dairy Milk Caramel Nibbles at £9 for 400g, or £2.25 per 100g. The same product can be bought on the high street for £1.38 per 100g.

Dispatches found a bottle of Jameson Irish whiskey advertised for £18.59 but at the till the reporter was charged £28.49 because they were not flying outside the EU.

The shops have small green squares on their labels that state: “Only for passengers travelling outside the EU.”

But the investigation found staff admitting that some customers were confused by the labelling system.

World Duty Free said: “Our airport exclusives include many unique, limited edition or gift items which are not available on the high street and are very popular with travellers.

“Our customers benefit from VAT and duty-free savings on thousands of products in our airport stores.”

The Times revealed last year that airport profits from bureaux de change had soared to more than £100 million a year as rates tumbled below one euro to the pound.

The newspaper’s investigation found that passengers at UK airports received markedly worse exchange rates than travellers at European airports because the owners of Heathrow and Gatwick had driven up rents.