The Road Safety Authority has confirmed that a data breach has occurred on the website for the new National Driver Licence Service.
The breach occurred on the Contact Us section of the website, which failed to refresh and retained queries, allowing other users to see that information.
The RSA said 721 people have been affected but that they do not believe there was any financial information submitted through the website.
It said it is currently reviewing each case and contacting the individuals involved to advise them of the breach.
It added that details submitted vary but an initial review indicates the majority are of a general nature.
The authority said it became aware of the problem this afternoon and has removed the page while it investigates the breach.
It has informed the Office of the Data Protection Commissioner about the breach.
RSA spokesperson Brian Farrell said the breach was "not acceptable" and it was being treated with "very, very high priority".
In a letter to customers, the RSA has apologised for the inconvenience and distress the incident has caused.
It said it is reviewing its process to ensure this does not happen again.