Ryanair is disputing Aer Lingus' claim that it would post a profit for 2008 and instead insists that the airline would incur "substantial" net losses.
Aer Lingus, the subject of a proposed Ryanair takeover, has insisted that new productivity deals with unions, lower fuel prices and a healthy cash reserve will see it turn a profit next year - a claim Ryanair vehemently contests.
"Unfortunately for Aer Lingus shareholders, the reality is that it has incurred substantial - as yet undisclosed - exceptional costs and companies have to pay tax, so the result will be another year of substantial net losses," says Ryanair chief executive Michael O'Leary.
"It beggars belief that Aer Lingus claims, just one week before its year-end, it does not yet know the exceptional costs for 2008 while still making a forecast."
Ryanair has published an open letter to Aer Lingus in which it is seeking clarification of several specific financial points, including any spending cap set on Aer Lingus' defence of Ryanair's takeover bid.