The airline's newspaper advert promoted fares from £25 one way, "all inclusive and with no hidden extras".

And it said that flights went from Belfast or London to destinations in France.

Lots of actual customers enjoyed low fare travel from that advertisement and we didn't have one complaint

Simon Lilley British European

But the Advertising Standards Authority (ASA) said the advert - which has since been withdrawn - was misleading because it implied the £25 fare was available for all destinations listed on the advert.

The ASA also upheld a complaint which challenged whether British European operated one of the advertised services, between London and Toulouse.

Changes made

British European said the small print in the adverts had made it clear that the £25 fare was not available to all destinations, and that "prices may vary by route".

But it said it had no plans to repeat the wording in future adverts.

And British European said the London-Toulouse service was operated by Air France.

The airline said it had a partnership with Air France which allowed it to sell Air France flights using its own flight numbers, which the company said was common practice within the industry.

British European said it had now withdrawn this type of advert.

General manager of marketing for British European, Simon Lilley, said he was annoyed to discover that one of the complaints had come from a rival low cost airline.

"I don't think the Advertising Standards Authority's role is a vehicle for organisations to complain about a competitor," Mr Lilley told BBC Radio Five Live.

"Lots of actual customers enjoyed low fare travel from that advertisement and we didn't have one complaint."