LIBERTAS FOUNDER Declan Ganley was listed for nearly a decade as a British national in official UK company records, before changing to Irish in 2006.
The nationality issue has arisen following bitter exchanges on RTÉ radio last week between Mr Ganley and Minister of State Dick Roche, when Mr Ganley denied that he had ever declared his nationality to be British.
The records for Ganley International registered with the UK Companies House listed Mr Ganley as a director, and his wife, Delia Mary as company secretary.
In 1995, Mr Ganley is first listed as a director of Ganley International - a company previously known as Acegrind.
Mr Ganley's date of birth is then listed as July 23rd, 1968, before his nationality is given as British and his occupation as a trader.
These details, accompanied by his home address in London where he was then living, remain consistent for the rest of the 1990s.
In February 2001, a handwritten entry for Mr Ganley again lists his nationality as British, although by then his home address had changed to Moyne Park, Tuam.
In 2002, the annual returns are again handwritten and again Mr Ganley's nationality is listed as British, while a London home address is listed on this occasion.
Questioned about the matter on Friday evening, Mr Ganley told The Irish Times: "Somebody must have made a data input error."
During a short conversation, Mr Ganley went on: "I resent anybody trying to deny me my nationality. I need to see what you are talking about.
"If somebody was in some office ticking a box in some file . . . I do not have a British passport.
"I am an Irishman, and I resent anybody trying to tell me that I am not," he commented.
Mr Ganley was born in London to Irish parents, who returned to live in Galway when Mr Ganley was in his early teens.
Under a long-standing dual recognition agreement between Ireland and the United Kingdom, British passport holders who are entitled to hold an Irish one can apply and obtain one.
"Any person who is entitled to obtain an Irish passport is not required to reject any other passport/citizenship they hold," the Department of Foreign Affairs said last week, in response to a general question about the rights of children, or grandchildren of Irish nationals born abroad to official Irish documents.
During bitter exchanges on RTÉ Radio 1's News at Oneon Thursday Mr Roche said Mr Ganley "likes to wrap himself in the tricolour whenever he faces any form of query or interrogation on issues like this".
Mr Roche then charged: "Why if you look at some companies you register yourself as an Irish citizen when it suits and register yourself as a UK citizen in other cases."
Interjecting, Mr Ganley declared: "I have never done that".
Mr Roche went on: "Mr Ganley you are now telling an untruth. I can prove you are not telling the truth - go have a look at your own company records Mr Ganley."
Last night, Mr Roche said: "Mr Ganley reacted viciously when it was pointed out on RTÉ that he had, on the occasion, chosen to describe himself on company registration papers as a British national.
"There is, of course, nothing wrong with being a British national.
"The point can fairly be made, however, that it is not on that Mr Ganley, who now wishes to proclaim himself as an Irish businessman, should choose to describe himself as British on UK company returns over a number of years."
Meanwhile, one of Libertas's key staff during the campaign, Naoise Nunn left his post last Friday to resume work on his event management business, though he insisted that his relations with Mr Ganley remain good.
Multi-millionaire businessman Ben Dunne, who came out against Lisbon in the days before the referendum, said he could now be persuaded to vote for it, if the Government explains it properly.
However, he said he was not persuaded by Mr Ganley, or Libertas: "I just don't have any time for the Libertas party or anything that they stand for. They're into . . . they're mixed up in too many things for my liking," Mr Dunne said.