The potential takeover has already been dragging on for five months after IAG initially made its approach, which was accepted by Aer Lingus in January.

However, the deal is entirely conditional on the Irish airline’s two major shareholders, rival Ryanair and the Irish government, agreeing to sell.

The Irish government, which owns a 25pc stake, has delayed making a decision for months and set up a dedicated committee to review the arguments round the sale.

The state has now received the report by the expert group, which could pave the way to the Irish government announcing its backing for the deal as soon as the next cabinet meeting on Tuesday, Reuters reported.

Paschal Donohoe, the Irish transport minister, has said that the government would “take great care and exercise great caution in examining the pros and cons to Ireland” of any offer.

Dublin has previously demanded that IAG extend its guarantee to keep Aer Lingus’s 23 Heathrow landing slots focused on Irish routes for ten years.

However, Willie Walsh, IAG chief executive, had told an Irish parliamentary committee that he could not offer more than five years.
The Irish government has also said that routes from Cork and Shannon must be protected. There are also concerns that guarantees could fall foul of the European Commission’s competition directorate.

Mr Walsh said last week that IAG was in “no rush” to complete the deal. "I'm perfectly relaxed about the timing. My board is very happy. Consistently I have said that this is a deal we would like to do,” he said.

Unlike UK takeover rules, there is no time limit for a bidder to make a formal offer. Ryanair has said that it will wait for a formal offer before making a decision but is widely believed to be a willing seller of its Aer Lingus stake.