A number of Ryanair advertisements promoting free or discount flights have been deemed to be in breach of advertising standards.
An advert by the airline published last month promoted 500,000 "free seats", subject to taxes and charges.
However, the Advertising Standards Authority of Ireland (ASAI) said use of word "free" to describe fares which were not free was misleading.
The ASAI wrote to Ryanair asking the company to explain its use of the word "free". However, the airline said as there had been no complaint from a specific consumer, it had no intention of replying to the authority.
A customer who complained that the flights offer did not extend to Brussels, despite being listed as a destination in the advert, also had their complaint upheld.
Ryanair responded that nowhere in the advertisement did it suggest that every route was included in the offer.
The airline was also deemed to be in breach of advertising standards for two e-mail promotions.
In one case, a cross-Border complainant said a promotion for 50,000 free flights, plus taxes, from "Glasgow" was misleading because the airline flew to Glasgow Prestwick, not Glasgow International.
The ASAI's complaints committee said advertisements stating a departure city served by more than one airport should state the airport's name to avoid confusing or misleading consumers.
It also said use of the word "free" should be limited to situations where there is no charge to the consumer.
In all, three Ryanair advertisements were the subject of complaints in the ASAI's latest complaints bulletin.
