Approximately 4,100 people are applying for a new passport on a daily basis, the Department of Foreign Affairs has confirmed.
Almost 70,000 passport applications are now in the backlog, an increase of nearly 20,000 since the end of March.
This is an increase on the Mid-April figure of 66,000 and the end of March figure of 50,000.
The passport office in Dublin is processing 3,600 passports a day, but this is still a shortfall of 500 on the numbers received.
Some 69,400 passport applications are currently in the backlog, accounting for a tenth of applications received annually.
The Passport Office processes 650,000 applications every year according to the Civil, Public and Service Union.
The Department said the average processing time was now taking 15 to 20 working days, but warned it was no longer possible to guarantee a turnaround time for the processing of passport applications.
The spokeswoman advised holidaymakers to check expiry dates before making plans and to submit applications in sufficient time before the intended date of travel.
“The public counters and out of hours services should only be used by those who have a necessity to travel for reasons of family emergency i.e. travel is necessitated by the death, illness or welfare of a family member,” she said.