The CAA launched an investigation into the online travel companies at the end of 2015 to look at price transparency issues after they failed to address numerous concerns raised by the regulator.

In particular, the CAA took issue with headline prices displayed on the website, saying they should be “achievable for consumers paying by a commonly used payment method”.

As a result, the sites have now changed their headline prices to display an all inclusive price when paying with a debit card.

The regulator also raised issues about Google AdWords search results as it should be clear to consumers which website they will be directed to when they click through from a Google search result.

Changes were made to eDreams’ Google AdWords search results to ensure it is now clear to consumers that the search result relates to eDreams rather than a specific airline.

Finally, the CAA tackled the overall website appearance, stating when consumers visit the third-party agent websites, “it should be clear they are on the website of the agent and not that of a specific airline”.

Changes were made to ensure it is now clear to consumers they are booking on the eDreams and Opodo websites rather than the website of a specific airline.

The CAA’s Richard Moriarty said: “Consumers spend a lot of time and money choosing and booking their holiday and have the right to clear and accurate information about how much they will have to pay and which company they are booking with. There are clear regulations in place for that very reason.

“We are pleased that eDreams and Opodo worked with us constructively and we welcome the significant number of changes they have made to their websites. These changes make it much simpler for consumers to be able to see the actual price of flights and holidays displayed on the sites – enabling them to compare options more easily.”

An eDreams spokesperson, said, “At eDreams and Opodo we are focused on making it as quick and easy as possible for the 17 million customers who book with us every year to find the best value and most convenient travel options. We have been working closely with the CAA and we’re pleased that they recognise the work we have done to make our customer experience smoother and clearer.

“We are now offering a new price display so that our customers can more easily compare the prices of their travel options, to continue getting the best and most convenient deals.”