Personal data on up to 20,000 people in Northern Ireland was put at risk by government bodies in the last year.
The justice system, central government and agencies were affected by breaches of information security, the Information Commissioners' Office (ICO) said.
Losing computer discs or misplacing laptops are among the ways confidential material can be endangered.
ICO assistant information commissioner Aubrey McCrory told Stormont's Finance Committee there had been 26 incidents in the last year.
"Individuals may accidentally or sometimes deliberately use information for the wrong ends. That also needs to be addressed through the culture within the public sector," he said.
There have been a string of high-profile information losses, including thousands of drivers' details sent from the Driver and Vehicle Agency (DVA) office in Coleraine.
Mr McCrory added such breaches were very high in people's list of concerns and were happening "again and again".
He said there had been 26 incidents in the last year affecting 15-20,000 people.
"I think it is significant in itself, that it is something that is addressed, that public concern is recognised and also the actions that are set out to be taken are taken and the public are reassured in terms of their information and importantly the public sector needs that information to be able to do its business."
Ian Paisley Jnr said the numbers involved were "minuscule" when set against the number of pieces of information which government handled and railed against unnecessary bureaucracy.
"At the end of the day if someone is downright careless, civil servants, all the legislation in the world can't legislate for either stupidity, carelessness, or just not paying proper due attention to their jobs, leaving a data card on a train, dropping a disc where they should not have dropped it, forgetting their laptop, having it stolen, all this money that is being paid into it, all this £20 million can't actually stop that carelessness."
In 2007 it was revealed two discs with personal details of 25 million people were lost by Revenue and Customs.
The UK government said the details of three million candidates for the driving theory test had also gone missing.
And the DVA in Northern Ireland lost the personal details of 6,000 drivers.
The data was on two discs and went missing after being sent to the Driver and Vehicle Licensing Agency (DVLA) headquarters in Swansea.