The Central Statistics Office has warned that the publication of census returns is strictly prohibited following a social media post containing data from the 1926 Census.
The CSO said a copy of the 1926 Census has been posted on social media and has asked that it be taken down immediately and not shared further.
"All Census returns from 1926 onwards are closed to the public for 100 years in accordance with Section 35 of the Statistics Act 1993," a spokesperson for the CSO said.
The records are kept away from public inspection for 100 years due to commitments on confidentiality as laid out in the act.
The CSO said unauthorised disclosure of personal data is also an offence under the Data Protection Act 2018.
Old census returns are important historical and genealogical records, with the 1926 Census being of particular interest as the first census undertaken by the newly established Irish Free State.
Returns from between 1926 and 1946 (and part of those for 1951) are held in the National Archives, but remain in control of the CSO.
Under the 100-year rule set out in the 1993 Act, the 1926 Census will be released to public inspection in January 2027.
Reports from the 1926 Census, published before 1935, are available on the CSO website.
Several 19th century returns were lost when the Public Records Office in the Four Courts was burned in 1922.
The 1861 and 1871 Census returns were deliberately destroyed, and the 1881 and 1891 returns were pulped in 1918.
The 1901 and 1911 censuses, which were taken under legislation which made no provision for confidentiality, remain intact and available.