The National Transport Authority (NTA) has been criticised for not including fadas in people’s names on Leap cards.
Conradh na Gaeilge, the Irish language organisation, has said that the omission of fadas is a breach of legislation governing GDPR.
However, the NTA has blamed "technical limitations" for the absence of fadas.
Speaking on RTÉ’s News at One, a spokesperson for Conradh na Gaeilge said until recently the law did not require the fada to be included.
Emma Ní Chearúil said that "while it might have been inconvenient or annoying, it was allowed."
However she said that under Article 16 of GDPR law, the omission or misuse of a fada is a breach.
Ms Ní Chearúil added that the failure to include special characters such as fadas does not only affect Irish people.
"Now that we have an increasingly multilingual and multicultural society, there is a huge proportion of our population who will have their names misspelled because of this.
"On a basic level it is a case of identity, your name is who you are and that deserves respect. It deserves to be treated as legitimate and at the moment it isn't always," she said.
She added that English is in the minority as a language that does not feature "special characters".
"You wouldn't see this in French or German so there isn't really an excuse why they can't provide an Irish language version," she said.
Meanwhile, the Ceann Comhairle has said that while he must remain outside of political matters, he personally prefers to have fadas used in his name in official documents.
Speaking on RTÉ's News at One, Seán Ó Fearghaíl said: "When I'm dealing with official Ireland I would particularly require it to be right, but I wouldn't lose sleep over the matter.
"It's unacceptable that the State cannot transact its business properly, completely and transparently with the people through our first national language," he added.