An undercover investigation by RTÉ Prime Time found that data showing the specific movement of tens of thousands of smartphones in Ireland is available to purchase.

Individual phones in the data could be tracked back to specific residential addresses after entering high-security prisons, military bases, and Leinster House, as well as sensitive locations like health clinics and mental health facilities.

The data available for purchase shows the minute-by-minute movement of phones, while the locations provided are specific enough to show movement within home addresses, as well as the patterns of life of the smartphone owner.

A large sample which contained the movement of 64,000 phones in Ireland over two weeks earlier this year was given to RTÉ Prime Time for free during the investigation, in which a team of journalists posed as founders of a newly-established data analytics and marketing firm.

The sample data was available to purchase from one company and the undercover RTÉ Prime Time team was told the data could be provided as a constantly updated feed, with a 24- to 72-hour delay.

The availability of the data has raised major worries about personal privacy, but also national and domestic security, including at the highest levels of the Department of Justice.

When asked about privacy concerns, sellers said a privacy breach does not occur because the owner of the phone is not identified.

They also noted that the smartphone owners would have given permission for the sale of the location data through the terms and conditions of installed apps.

However, RTÉ Prime Time was able to use the data to quickly identify the home addresses and routines of life of specific individuals by examining the tracks of devices which entered certain locations then returned to residential addresses.

One was a person who works in Leinster House, in the parliamentary office of government TD, Barry Ward. The individual did not want to be identified but did confirm the information in the dataset was accurate.

The data showed that individual’s routine and exact movements, including their routes into and out of Leinster House, when they were in their local supermarket, location of weekend activities, and times they returned and left home.

Mr Ward told RTÉ Prime Time: “What has really shocked me is the extent to which you can take that data parcel, break it down to an individual, trace the individual’s movements to the extent that you can identify where they live, where they work… or where they go on a day-to-day basis.

“The notion that the information about their movements is free and available to buy for anyone is frightening, totally inappropriate, and definitely dangerous.”

In a statement, the DPC said: “The DPC first became aware of this matter when contacted by Prime Time and we are extremely concerned by it.

“Location data can reveal a significant amount of information about individuals, including information about an individual’s habits and personality, and information that is inherently sensitive. Information about an individual’s location can also pose a serious risk to their security and wellbeing.

“We are currently working to identify the data broker in question and if they are headquartered in Ireland, we will take action ourselves. However, if they are headquartered in another EU country, we will engage with the relevant data protection authority to deal with the matter.”