Almost one-third of State IT projects commenced in the last two years have either gone over budget or are projected to do so.
The finding is included in an investigation undertaken by the Dáil's Committee of Public Accounts (PAC) after the Arts Council spent €6.7 million on a complex IT project that was later abandoned.
The commitee will discuss the results of the investigation today.
Of the 220 IT projects undertaken by Government departments and State bodies under their aegises since the start of 2024, 34 completed initiatives had an overspend while there are 33 ongoing projects with a projected overspend.
Seventeen completed schemes had overspends of more than 10%.
The gross overspend across Government departments was €40m. However, when offset with projects that came in under budget, the net overspend was €1m.
PAC members say they are concerned by details of several initiatives, including plans to implement contactless ticketing for public transport in the Greater Dublin Area.
The National Transport Authority's Next Generation Ticketing project aims to allow passengers to pay for buses, trains and trams using bank cards, mobile phones and other smart devices by 2028.
Correspondence provided to the committee shows that - as of last August - €12.9m had been spent on a project that started in August 2021.
The initiative has an estimated cost range of €228m to €269m, with a target completion date of July 2028.
"Particularly alarming is the Next Generation Ticketing project - with very limited detail on what has actually been delivered to date," said Sinn Féin TD John Brady, the committee's chair.
The NTA told the committee that it adheres to established governance structures and its most recent external audit awarded it the highest rating of "substantial" controls.
Read more:
Review after Arts Council's unsuccessful IT project
Contactless ticketing to come into effect in 2028
The investigation also highlights how a €4.3m Fiosrú case management system project was abandoned due to contractual issues, with almost €500,000 already spent.
The Department of Justice told the committee that the initiative is being reassessed to ensure value for money.
"The most serious example here, I believe, is the collapse of the Garda Ombudsman/Fiosrú case management system", said Fine Gael Dublin Bay South TD James Geoghegan, upon reviewing the findings.
A new DNA information management system for Forensic Science Ireland had been due to cost €760,000 but rose to €2.7m upon completion.
"The original business case greatly underestimated the complexity of the project and resources required to deliver on requirements," noted the Department of Justice.
An affordable childcare ICT scheme exceeded its original estimate by €3.5m - or 49% - to reach a final cost of €10.6m.
The Department of Children said the initial proposal under-estimated the necessary specifications and consequent costs of some of the items involved in the project.
"What has emerged is a deeply concerning pattern of consistent failings across Government. Gaps in expertise, weak oversight structures, poor project management, and wholly inadequate initial cost estimates", said Mr Brady.
"The findings show that major ICT projects are repeatedly running over time and over budget, with insufficient accountability mechanisms in place.
"This will be an area of continuous monitoring for the committee going forward," he added.
