The staff shareholding group at Aer Lingus has written to the Takeover Panel accusing Ryanair of making inaccurate claims in the offer document the airline issued to shareholders earlier this week.

The Employee Share Ownership Trust (Esot) said it was writing to the panel after it asked for clarification on what kind of benefits Ryanair's €1.4 billion offer would provide to staff.

If the Takeover Panel sides with the Esot and Aer Lingus, Ryanair could be forced to amend its offer document.

So far, Ryanair has claimed that Aer Lingus Esot members would realise on average more than €60,000 each if they accept the Ryanair offer.

Ryanair claims that staff at Aer Lingus stand to benefit by €220 million in total.

In a letter, the Esot described the €60,000 calculation as inaccurate and said the figure was €38,864.

It also refused to comment on the taxation elements of the Ryanair offer: "We note also the reference to members being able to 'realise this money on a tax-free basis', by reinvestment in Ryanair shares. We make no comment on this, other than that we are examining this part of the announcement."

Aer Lingus itself said Ryanair's claim about €60,000 was seriously misleading.

Its statement said: "The facts are that the Employee Share Ownership Trust (Esot) has approximately 4,665 members.

"After allowing for the Esot's borrowings, the offer is worth an average of approximately €32,500 per Esot member.

"This inaccuracy had been drawn to the attention of Ryanair."

Ryanair stuck by its claims and said the only offer from Aer Lingus itself was job cuts.

Michael O'Leary, Ryanair's chief executive, said: "If these developments are true, it is clear that the best interests of Aer Lingus employees are served by accepting Ryanair's generous offer, because their future as a small, uncompetitive, stand-alone Aer Lingus looks even bleaker today than it did yesterday."

This is a reference to plans by Aer Lingus to cut costs at the airline which were announced to staff during a meeting this week, although specific details have yet to be released.