The decision by Aer Lingus to end the Shannon-Heathrow service will sever connections to the west of Ireland from 46 cities across the world not served by other London airports.
The claim was made in a document, Business Case, for the retention of the route drawn up by the Atlantic Connectivity Alliance (ACA), a coalition of business, tourism, union and other interests in the mid-west.
The document was sent to Ministers yesterday ahead of a Cabinet meeting today discussing the Shannon issue.
The publication of the report, which the ACA claims is the first time the case has been made on a factual basis of the very significant impact that the Aer Lingus decision will have on the region, yesterday coincided with both the Shannon Airport Authority (SAA) and airline Bmi (British Midland)playing down a report that the airline was set to replace Aer Lingus on the Heathrow route.
The Shannon authority said it was in talks with a number of airlines, including Bmi, but these were at an early stage. "The talks are complex in nature, and the authority is denying that any advanced talks have taken place. It is an ongoing process."
A Bmi spokesman said the company was aware of speculation linking the airline to the Shannon-Heathrow route, but it had a policy of not commenting on potential route development.
Launching the Business Case report, ACA chairman Cllr John Brassil said he hoped the document would "bring an end to the campaign of misinformation regarding the move, and facilitate the commencement of real and honest debate on what is an issue that has implications for not just the region but the entire nation".
In his message to Ministers, he said: "The choice is simple: you can ignore the customer and the west and force through the decision and live with the serious consequences.
"Alternatively, you can listen to the voice of some of Ireland's top wealth-creators, focus on solving the core problem of connectivity, work with us and deliver a win-win solution for our country."
The document says Heathrow is the west's closest gateway to the global economy serving 200 destinations.
The closure of the route "will sever the connections to the most extensive, effective, existing network of air connections to global markets, cutting off access to 46 cities not served by other London airports".
The report challenges the commercial rationale behind the Aer Lingus decision, claiming that "all factors impacting on the decision have not been adequately considered: profitability; cost base; 350,000 passengers abandoned at the drop of a hat; billions of investment under way in the Atlantic corridor; catchment area underestimated; corporate responsibility and damage to the Aer Lingus brand".
Meanwhile, chairman of Shannon airport Pat Shanahan said yesterday he was confident that the Government would be allowed by the EU to provide State aid to support the development of new routes out of Shannon.
After holding talks with senior officials at the European Commission in Brussels, he said he was satisfied the Government could establish a multimillion euro incentive package.
"Britain has a route-development fund worth € 36 million established for Wales, Northern Ireland and Scotland, and the Maltese have a scheme worth €58 million. I am satisfied a fund is feasible for Shannon under current EU guidelines."