For a frugal airline that relies on getting as much free publicity as it possibly can, Ryanair and its chief executive Michael O'Leary might be considering a glass of Jameson to go with his pint of Guinness today.

The Irish budget carrier has been involved in a spat with Britain's ASA - the Advertising Standards Authority, which Ryanair has dubbed the Absolutely Stupid A***holes - for months as it continues to test the boundaries of acceptable advertising.

With the ASA attempting its latest clampdown on the errant airline - it has found Ryanair in breach of its rules seven times in the past two years - Ryanair took the unusual step last week of complaining to the Office of Fair Trading that it was being harassed, an action seen by O'Leary-watchers as another stunt.

However, the ASA is now formally referring Ryanair to the OFT, stating that the airline has "persistently misled consumers".

Such an official complaint to the OFT is rare, even if the subject of the argument against Ryanair may be familiar to Ryanair users.

The ASA says Ryanair has failed to state full prices including hidden charges and taxes; exaggerated details about available flights on its apparently special offers; failed to reveal restrictions on travel; and made misleading comparisons with competitors.

Ryanair could ask the OFT for countless other offences to be taken into consideration, such as using images of French President Nicolas Sarkozy and his wife Carla Bruni without their permission and using an image of a model raunchily dressed in school uniform with the tag line "hottest back-to-school fares".

"It is very disappointing but absolutely necessary that we have had to take this course of action," said ASA director general Christopher Graham.