The changes come following a near year-long investigation into the two OTAs, which are owned by the eDreams Odigeo group.

It was triggered after both companies failed to address numerous concerns raised by the regulator over their websites and pricing practices.

The investigation saw the gathering of evidence and information from a range of stakeholders, including consumer groups, as well as the CAA’s own analysis.

This led to concerns about the way information and prices were presented to consumers and has led to undertakings from both brands that they would change their websites to ensure prices are more transparent.

CAA director of consumers and markets group 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.

“We will continue to monitor the practices of airlines and leading travel companies to ensure consumers have access to clear and accurate information on prices. And where we have evidence of misleading practices by companies, we will not hesitate to take action where necessary to protect consumers.”

A spokesperson for the two companies 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.”