DUBLIN (Reuters) - The number of Irish passport applications by British citizens has almost doubled since June’s vote to leave the European Union and the rate of enquiries is continuing to accelerate, Ireland’s foreign office said on Wednesday.

Anybody born in the Irish Republic or Northern Ireland, or with an Irish parent or grandparent, is entitled to an Irish passport - a total of about six million British citizens. They are able to hold dual citizenship.

Post offices ran out of passport forms and embassies fielded thousands of calls in the days following the June 23 vote and data on Wednesday showed 21,500 Britons have applied since July compared to just under 11,000 in the same period a year ago.

Applications by Britons trying to hang onto EU citizenship via a passport from their nearest neighbour have increased each month since the vote and rose 120 percent year-on-year in September, the foreign office said.

Registrations for Irish passports in Northern Ireland, whose citizens can hold both an Irish and British passport as the province is part of the United Kingdom, rose by 68 percent over the same three-month period.