The rise follows an in-depth review by the CSO of homicide data going back to 2003 and an examination of 41 cases by gardaí between 2013 and 2015.
There have been no official crime statistics for a year after the CSO decided to defer publication over the quality of homicide figures.
The CSO said it has now decided to publish homicide figures “under reservation”, meaning it continues to have concerns over their quality.
The CSO will next Wednesday publish a table of previously recorded homicide figures and along with that produce updated data.
The move by the CSO is separate to a review by the Policing Authority and the Garda Síochána regarding the classification and investigation of homicides.
Olive Loughnane, a CSO statistician, said the new data will show a “significant increase” to previous homicide statistics, and that the change is “quite stark”.
Ms Loughnane said this was due to two sets of changes, the first being the Garda review of 41 cases between 2013-2015 that resulted in 12 crimes being upgraded to homicide.
She said that when the CSO learned of this internal review, they started conducting a detailed examination of homicide incidents, and identified separate issues.
Ms Loughnane stressed that the homicide figures were being published with a heavy caveat: “There is a public interest in resuming publication, but it is important to state that they are being published in a new category of ‘under reservation’ — that there are serious deficits in the data.
“We have taken the decision to publish the best available data in order to address the information void.”
She said there had been a lot of co-operation with the Garda Data Quality Team.
She said there was an ongoing review by gardaí of homicides going back to 2003 which could result in further revisions.
Meanwhile, a Garda public attitudes survey has found that only 35% of people thought the Garda Síochána provided a world-class service (down 5%) and just 38% believed it was well managed (down 7%).
In contrast, 87% thought members of the force were friendly or helpful, and 88% had mid-to-high trust in the organisation.
Some 70% were satisfied or very satisfied with the service provided by the force.
Some 72% perceived national crime to be either a serious or very serious problem, but only 19% said the same about their locality.
Satisfaction rates among victims of crime who reported it to gardaí fell 7%, to 55%. Deputy commissioner John Twomey described that particular finding as “very concerning”.