Michael O'Leary is expected to come out strongly against comments made on Friday by Aer Lingus chief executive Dermot Mannion telling the unions that the 1.5bn takeover bid represents bad value for shareholders.

Last Friday the Central Representative Council (CRC), an umbrella body for unions at Aer Lingus, claimed that the airline's ESOT members would "gain an average of just 4,000 each if Ryanair's takeover bid succeeds".

The CRC based its claim on the 30 cent difference between what it says is the "fair value" of Aer Lingus shares at 2.50, and the offer price of 2.80. It also claimed that Aer Lingus employees would have to retain that 4,000 sum as Ryanair shares to avoid "large" tax liabilities.

The CRC added that in the past three years Ryanair's stock rose 21%, while British Airways' rose 121% and the European sector rose 85%.

However, in the past seven years . . . a more typical investment period . . . Ryanair's stock rose over 376%, while British Airways' climbed just 33%.

Asked by the Sunday Tribune on Friday if the the government should shoulder responsibility for failing to set the flotation share price high enough, Mannion declined to comment directly. He and the Aer Lingus board described the 2.80 share offer by Ryanair as "derisory".

He batted away suggestions from the Sunday Tribune that if the current offer is derisory, then the offer price should be considered appalling. Asked what he thought would represent value rather than a "derisory" price, he said "he could not conceive what circumstances" in which a Ryanair bid would ever become acceptable to the board. No price is high enough, it seems.

If Ryanair decides to improve its offer, Mannion may soon discover what is acceptable to Aer Lingus shareholders. NCB analyst John Sheehan has previously said that Ryanair could bid as much as 3.50 per share and the deal would still make financial sense.

ESOT members will be balloted in coming weeks and seem destined to have to base their decision on conflicting financial information that has failed to identify correctly the true monetary benefit to them of a successful takeover of Aer Lingus by Ryanair.