One of Many ProSome UK residents are entitled to an Irish passport if their parents or grandparents were born in Ireland.
In 2015, the year before the Brexit vote, more than 46,000 applications were lodged from Britain - excluding Northern Ireland.
By the end of 2017 that number had nearly doubled to 81,000.
In an earlier version of this story, the BBC wrongly reported there had also been a surge in the number of rejections of British applicants.
A discrepancy between the number of applications made and passports issued through the London embassy amounted to some 15,000 people. However, Ireland's Department of Foreign Affairs said that figure did not represent the number of passport applications refused.
Instead it reflects the fact that not all applications from residents are submitted via the London embassy, it said.
The actual number of rejected applications is not clear. Applications can be rejected for a range of reasons including incomplete applications or uncertain identity.blems/Challenges Caused by Brexit