The demand for Irish passports hit record levels last month, with one in three applications coming from Great Britain and the North.
New figures show more than 112,000 people applied for an Irish passport in March, the highest ever number in a single month.
As the original deadline for Brexit approached, the Department of Foreign Affairs was also flooded with 4,800 phone and 1,500 online enquiries every week.
Paper applications from Great Britain and the North from January to March were up 103pc and 71pc respectively on the same three-month period last year.
There were 58,000 paper applications from the North and 41,000 from mainland Britain.
Tanaiste Simon Coveney has urged families to check their passports ahead of the summer holiday season to ensure they are still valid.
"Every year we see hundreds of families who end up spending thousands of euro rebooking flights because a day or two before travel they realise one of the children's passports is out of date," he said.
"We have expanded the online service to allow for both child and adult renewals.
"I would ask anyone travelling to take the five minutes to check the family passports ahead of the busy season of May, June and July."
The spike in demand began in January when 100,400 applications were received.
This continued with 100,500 passport requests in February before a big jump last month.
For people in Northern Ireland and Great Britain, an Irish passport will ensure they still have open access and full employment rights in other EU countries after Brexit.
The UK was due to leave the EU at 11pm on March 29, but this has been put back twice and possibly will not happen until October 31 at the earliest.
Before the first quarter of this year, there were only two months over the past five years when the passport application figure exceeded 100,000.
In 2018, there were 850,000 applications, but based on the current trajectory, the Department of Foreign Affairs is planning to deal with 1.1 million requests this year.