Ryanair has admitted defeat in its renewed takeover bid for rival Aer Lingus, but vowed to fight the decision in the courts.
The low-cost carrier said it had been notified by the European Commission that the 694 million euro (£596.7 million) buyout plan would be rejected.
Ryanair claimed European chiefs were holding it to much higher standards than any other EU airline.
"It appears clear from this morning's meeting that no matter what remedies Ryanair offered, we were not going to get a fair hearing and were going to be prohibited regardless of competition rules," Ryanair spokesman Robin Kiely said. Ryanair said it was told of the decision at a state of play meeting with the EU Commission.
The takeover plan - a third bid by Michael O'Leary for Aer Lingus - appeared to have been boosted last week when Flybe agreed a plan to fly 43 of Aer Lingus's short-haul routes, easing competition concerns.
There had also been a commitment from the IAG airline group to run overlapping Aer Lingus/Ryanair routes between Dublin and London Gatwick to ensure competition.
Mr Kiely said: "Given Ryanair's remedies package clearly addresses every issue raised in the EU's Statement of Objections, any decision to prohibit would be manifestly unfair and in contravention of EU competition rules.
"This decision is clearly a political one to meet the narrow, vested interests of the Irish Government and is not based on competition law."