A border trader has predicted three-hour queues of southern shoppers heading for Northern Ireland after a missed opportunity budget.
Dundalk is 14 miles from Newry in Co Down and could be hardest hit by Brexit and the plummeting value of sterling.
The flow of shoppers north has increased since the Leave vote on June 23 as the value of the euro rises.
Most Irish people should have an extra €5 (£4.50) in their pockets every week after an Irish budget tempered by Brexit fears.
In its first spending plan since the UK voted to pull out of the EU, Dublin revealed it is diverting hundreds of millions into future-proofing the country against the fall-out.
The war-chest funding left Finance Minister Michael Noonan with less to give away in a €1.3 billion (£1.2 billion) package, with three times as much on spending as tax cuts.
Paddy Malone, a chartered accountant in Dundalk in Co Louth, said traders had pressed in vain for regeneration measures and rate relief.
“We all remember 2009 when sterling was against us, we saw massive two-hour queues into Newry, we are heading in that direction if sterling continues to weaken,” he said.
The value of sterling has fallen since the Brexit vote and Mr Malone warned if the euro changed hands for 90p Dundalk traders would really suffer.
He hailed the decision to keep the hospitality and tourism VAT rate at 9% but said any gains could be wiped out by currency fluctuations.
Mr Malone, who represents Dundalk Chamber of Commerce, said traders had been pressing for participation in the Living City Initiative which focuses on regenerating commercial areas.
Kilkenny in the south east has benefited from a similar measure.
Mr Malone said: “We are three times the population of Kilkenny and much more in need of urban regeneration.
“We also asked for a rates subsidy from the Government but there is nothing there.”
He added: “The retail sector in Dundalk is going to be severely handicapped and there should have been some measures taken.”
He noted those travelling north had to pay to exchange currency.
“You then spend money in the cafeteria after spending three hours in a queue and you lose the time wasted in a queue.
“When you add it up it may not be worth killing yourself for the 30 or 40 quid that you save – you will probably blow it in the cafe.”
He said the retail sector in Dundalk was the area’s single biggest employer.
“By shopping outside Dundalk you are not helping employment,” he added.