The Dublin District Court was previously told this information was of “potential risk to the Irish State”.

The 45-year-old, who has been in Ireland since 2002 and lives in Dublin, was arrested at Dublin Airport last Thursday by the Garda Special Detective Unit.

Mr McKeeffe, who changed his named in Ireland by deed poll, was about to fly out on a one-way ticket.

The SDU, the force’s State security unit, arrested him under the Theft and Fraud Offences Act 2001 and the Official Secrets Act (OSA) 1963.

Mr McKeeffe told officers he was flying to visit his family, in the Donbas region of eastern Ukraine.

The SDU confiscated €5,600 in cash the man was carrying and took his mobile phone for examination.

Charged last Saturday, Judge Máire Conneely directed the state the accused was allegedly supplying information to could not be published. In addition, she directed the name of the department where he worked and his home address should not be published.

He was denied bail and remanded in custody to Cloverhill Prison, to appear before Cloverhill District Court on Tuesday morning.

During a brief hearing on Tuesday, barrister Aisling Ginger-Quinn, for the accused, said a High Court bail application was “in progress”.

She said they consented to a four-week remand, to June 30, for DPP directions in the case.

Judge Alan Mitchell told the accused if he is given bail by the High Court, he must turn up in person at Cloverhill District Court on that date.

If he is refused bail, he will appear again by video-link.

At last Saturday’s hearing, Detective Sergeant Shay Palmer of the SDU told the court the accused was charged under Section 9 of the Theft and Fraud Offences Act, relating to accessing a computer for unlawful gain.

He said conviction for this offence, on indictment, attracted a possible sentence of up to 10 years.

He said there was the possibility of further charges, under the Criminal Justice Corruption Offences Act and the Official Secrets Act.

Mr McKeeffe has not yet indicated a plea.

During a bail hearing on Saturday, Det Sgt Palmer said they were objecting to bail, based on the seriousness of the offence, the nature and strength of the evidence, and the significant admissions the accused made in interviews.

The SDU officer said the charge related to obtaining, transferring and communicating data from the department to “foreign intelligence service” for personal gain.

He said the accused was intending to fly out of the country last Thursday to meet with his contact and “share confidential information” that was of “potential risk to the Irish State”.

He said the SDU conducted a search of the man’s home in Dublin and his office in the department. Mobile phones, laptops and desktops were being technically examined.

He told the court the accused had previously flown out of the country under different names. In total, he had five names and three different passports.

He said the accused made admissions while being interviewed.

Judge Conneely rejected the application for bail, holding there was a flight risk.