Nearly 300,000 jobs depend on Ireland’s relationship with the UK, retailers have warned.
Irish shops have already seen a dip in consumer confidence and loss of sales because of the devaluation of sterling, Lorraine Higgins from Retail Excellence Ireland added.
Counterparts in Northern Ireland said leaving the single market and customs union following a hard Brexit would be a backwards step.
Ms Higgins said: “Disentangling Ireland from the UK is the most brutal break-up and we need to ensure that we have the best possible plan to safeguard Irish retailers and the 282,000 jobs and 100,000 businesses dependent on the relationship.”
Retail Excellence and Retail Northern Ireland jointly presented to the Oireachtas Committee on the Good Friday Agreement.
Ms Higgins, head of public affairs at Retail Excellence, added: “For many local businesses this is a difficult and uncertain time.”
Retail NI chief executive Glyn Roberts said retailers needed to focus on international visitors.
“Both our organisations are working in partnership to ensure that policies are put in place to support what is the island’s largest industry by employment.
He said governments in Belfast, Dublin and London should begin the process of establishing a new one-hour fast train service between Dublin and Belfast, a “game changer” for the all-Ireland economy.
Mr Roberts added: “The bottom line is that Brexit should not result in any barriers in trade and on free movement across the border.
“It clearly is a major problem not having an Executive in place to argue our case in these vital Brexit negotiations.
“We urge all the political parties to redouble their efforts to secure agreement for a new administration.”