Business group Ibec has warned that a new economic order lies ahead for Ireland as the UK formally exits the European Union today.
Ibec has predicted that Brexit will remain at the top of the country's agenda in 2020.
Danny McCoy, Ibec's chief executive, said that while the catastrophic implications of a no-deal have been avoided, Brexit was always going to be an exercise in damage limitation.
"Even with an orderly UK exit that goes some distance toward mitigating the potential risks to the all-island economy, we will ultimately end up in a worse place than where we are now," Mr McCoy cautioned.
He said that as a result of Brexit immediate challenges remain on the horizon for Irish business.
"The new arrangements for Northern Ireland are complex, and many of the specific details of how they will work in practice still need to be worked out," he pointed out.
Mr McCoy said the current deal does not deliver the same economic benefits for Irish business as the previous all-UK 'backstop' proposal, which held out the prospect of close north-south and east-west trade and regulatory alignment.
He said this could have significantly negative economic implications for Ireland in due course.
"We have also been left with short, overly ambitious timelines to agree a future trade deal, which do not reflect business realities," he added.
Elsewhere, the British Irish Chamber of Commerce said the end of the UK's membership of the EU tonight would be witnessed with a heavy heart as joint membership had helped business, trade and cultural links prosper between the islands.
"While businesses will welcome the orderly Withdrawal of the UK from the EU, they must not become complacent and think that Brexit is now done," said John McGrane, Director-General of the chamber.
"This most difficult part of the process has yet to begin and could result in a permanent and significant change to how we do business and trade with each other."
"The coming negotiations are going to be tough, but the British Irish Chamber hopes that a more practical approach will emerge from both sides that will take account of legitimate business interests and concerns."
Chambers Ireland said it is with a sense of suspended disbelief that as the UK departs, businesses in Great Britain, Northern Ireland, Ireland and the rest of the EU have no idea what they now need to prepare for at the end of the transition period.
"The unilateral dismissal by the British Government of the mutually agreed option in the Withdrawal Agreement to avail of a two-year extension to the transition agreement must also be taken seriously," said Ian Talbot, Chambers Ireland chief executive.
"As the negotiations for phase two now commence, the realisation of the compromises and concessions required to reach agreement on specific issues will become very real, very quickly and time is on nobody's side."
"The cost to business, and the resulting impact on employment and taxes, of this ongoing uncertainty is unquantifiable."
The negotiation and ratification of a comprehensive and ambitious Free Trade Agreement will be a challenge, the organisation added, particularly as there is no precedent for this kind of negotiation.
