Holyhead Port will not be reopening until at least January 15, it has been announced.
The port's operator, Stena Line, said all ferry services to and from Dublin are cancelled until this time.
The closure of the port and ferry services will likely result in Christmas parcels travelling to and from Ireland being delayed until after the festive season.
It had been announced after Storm Darragh that the Port of Holyhead was to remain closed until December 20, with all services cancelled until then.
Taoiseach Simon Harris said on Monday the “seriousness” of the damage was becoming “more apparent as the days go by”.
It says passengers booked to travel from December 20 can transfer free of charge to an alternative route run by the shipping company.
Stena Line is offering sailings for passengers and freight from Dublin to ports in Birkenhead and Fishguard.
A new freight route from Dublin to Heysham has also been added to assist the continuity of trade flows, along with additional sailings on the Belfast to Cairnryan route this weekend.
The company apologised for any "inconvenience caused", adding it is doing "everything in its power to mitigate the effects of the closure on passenger and freight traffic".
Upon the announcement that Holyhead would remain closed, the Irish Road Haulage Association (IRHA) said it would need urgent Government support to keep the country supplied in the short-to-medium term.
It said that before the closure, there were 10,000 freight vehicles moving in and out of Holyhead per week at this time of year, which means significant redeployment and longer timelines for logistics companies. This freight accounts for 60% of the goods coming into Ireland.
The IRHA said one of its members has a fleet of 80 trucks in and out of the UK each week, and is losing €300,000 a week due to Holyhead’s closure, while drivers and vehicles are lying idle as they remain stuck at Holyhead.
“The statement that the port will not re-open until the mid of January has a huge impact on the industry and they are calling for financial support from the Government as a matter of urgency, not February or March but now,” IRHA president Ger Hyland said.
“There are only three island nations in the EU that are Ireland, Cyprus and Malta and Government needs to treat this as an emergency and assist us in this huge challenge we are facing to keep Ireland supplied and hence our fleets on the road.”