Ryanair boss and major Aer Lingus shareholder Michael O'Leary has said any approach by British Airways to buy into the ailing airline would be aimed at capturing its lucrative Heathrow airport slots.

He also warned that "nobody else" can take overall control of Aer Lingus without Ryanair's agreement.

In an interview with the Sunday Tribune, O'Leary said he would have "no difficulty" working with BA chief executive Willie Walsh – who is a former head of Aer Lingus – were he to buy a stake. But he said the only serious offers had come from his company, and had been rebuffed by the government. Ryanair holds a 29.8% stake in Aer Lingus.

"If the government is willing to consider an offer from Willie Walsh, it has to ask itself what does it deliver for Ireland. The answer is higher fares... it will also just take Aer Lingus's Heathrow slots. This would be the case if any overseas airline were to buy Aer Lingus," he said. "We've been quite clear on this: the future of Aer Lingus is as a low-fares airline."

O'Leary's comments come amid speculation that management at Aer Lingus may convince the government to sell some or all of its 25% stake to BA in order to ensure a "tie-up" between the two.

Aer Lingus's current chief executive Christoph Mueller has indicated that he is interested in selling a stake to a larger airline.