The Irish government has been forced to hire 200 extra workers in its passport office as British citizens, worried about the UK departing the European Union, seek Irish passports in record numbers.

Irish Foreign Minister Charlie Flanagan said on Monday there has been a huge renewed interest in Irish citizenship this year.

He said: "We've had an unprecedented level of applications. We've had in excess of 200 new staff on a temporary basis in our passport office.”

"There is a heightened interest in Irish passport applications and Irish citizenship."

While Flanagan diplomatically refused to confirm it was from British passport holders, the fact is that the Brexit vote coincides with the huge demand.

Recent opinion polls in Britain have shown the “leave” side up to seven points clear in the referendum to be held on Thursday, June 23.

If Britain departs the EU its citizens will face customs and passport controls in every EU country as well as a large dropoff in subsidies for many key programs.

British leader David Cameron agreed to the referendum to placate his right-wing critics in the last election, which he won easily as it turned out. Immigration has become a core issue in the referendum with the number of migrant workers coming in through EU countries a source of major concern for the British.

Ireland is worried about a British withdrawal, especially as it affects the North where passport controls have long disappeared making the whole island far more accessible.

Ireland’s leader Enda Kenny was in Belfast on Monday seeking to stoke up the “remain” vote which is also supported by Sinn Fein.

The irish government is also making a major effort to influence the 500,000 Irish citizens who live in Britain to vote.

As opinion polls show “leave” side winning, Irish passports a hot commodity.Eamonn Farrell/Photocall Ireland