Ryanair claimed the website had granted a non-exclusive licence to momondo to display its fares for price comparison purposes, along with other websites including Skyscanner and Dohop.

The airline said it revoked its licence after momondo displayed links to “unauthorised websites”, which Ryanair claimed “unlawfully mis-sell Ryanair’s low fares”.

Pia Vemmelund, managing director for momondo, said in response: "Our primary purpose has always been to show the lowest available price to provide our users with transparency.

"Therefore, we won’t compromise on that transparency by taking out specific travel agencies from our search results just because an airline like Ryanair tells us to. That would be against our principles.

"We can confirm that we no longer have a license agreement with Ryanair, but we cannot confirm a breach of contract or that we agreed to exclusively show Ryanair prices through Ryanair’s website only.

"So, we continue to show Ryanair flights when these are sold through travel agencies, and we’re happy to continue to show our users the lowest prices and offer transparency."

Meanwhile Ryanair has been engaged in several legal cases across Europe against websites such as Opodo and eDreams and it has commenced legal proceedings in the Irish High Court against both Google and eDreams.

In March, the UK Advertising Standards Authority found that eDreams and Opodo’s advertising on Google was “misleading” consumers and breached the CAP code (the UK Code of Non-broadcast Advertising, Sales Promotion and Direct Marketing), while the CAA this month told eDreams and Opodo to change their Google adwords practices, website appearance and headline prices, following submissions by Ryanair.

Ryanair said it had “no issue with OTAs who display Ryanair’s fares in a transparent manner”, and urged all of its customers to book directly on the Ryanair.com website.