Meanwhile, Ryanair's chief executive Michael O'Leary has said that the airline would continue to be a long-term shareholder in Aer Lingus. "It's our contribution to the nation. We add to the jollity of the nation by going after Aer Lingus."

He said, however, that it was unclear whether it would bother exercising its voting rights. When asked by the Sunday Tribune whether he wanted a seat on the board, O'Leary replied: "would you want to be there? God, imagine sitting down with that lot".

He also indicated the possibility of launching another takeover bid in the future was one reason why Ryanair had decided to keep its shares in what described last week as a "third-tier carrier" without a bright future.

"There is a business case for us. Look, we can buy this thing, we can turn it around, we can make it much lower cost, we'd make it lower fare and we'd make more profit out of it."

Meanwhile, aviation analyst Stephen Furlong of Davy Research has suggested that there may be other, less apparent, reasons why Ryanair had decided to retain its stake.

"From a Ryanair perspective, no other airline or trade player will try to buy Aer Lingus because they have a stake, " he said.

"It was also a good financial investment at the price they bought their shares at."

Aer Lingus executives are determined, however, to remove Ryanair from its share register and a spokesman for the company said that it was considering all options as to how it could force Ryanair to divest its stake.

His comments come days after the airline's London-based legal advisers Linklater said that Ryanair's stake would "be the subject of a separate process".

However, competition law experts believe that the airline's attempts to force Ryanair to give up its stake will be unsuccessful, particularly as both the European Commission and the Irish Competition Authority have said that they don't have the power to order it to do so.

One legal source said that, as Ryanair did not have any control of the airline, Aer Lingus's best chance to force a divesture would come if Ryanair attempted to buy another asset in the aviation sector.

In that circumstance, the airline could lobby the Competition Authority or the Commission to force Ryanair to sell its stake before the purchase could go through.