TWO firms building stakes in Irish Continental Group have confirmed that they now collectively hold 18.3% of the business. The news is being seen as a killer blow for the E470m ($631m) management buyout offer for the Irish ferry operator, tabled by chief executive Eamonn Rothwell. Irish newspaper reports state that Mr Rothwell and his colleagues are unlikely to come back with an improvement on their E18.50 per share unit bid. But his media representatives said today that there will be no formal comment on that claim unless a concrete rival proposal does eventually emerge. According to the Irish Examiner, citing unnamed sources, Doyle Group and One51 may take up to six weeks before making a formal counterbid, with the due diligence process commencing this week. The two firms have indicated that they are considering a bid at not less than E20 per share unit [correct], valuing ICG at over E500m. There is speculation that One51 sees the bid primarily as a property play. That company owns a small port at Greenore in County Louth. If ICG operations were to switch there, around 33 acres of land close to Dublin would be freed up.