The Data Protection Commission has written to Sinn Féin to seek more information about reports that the party has compiled a database containing personal information of millions of voters.

In the letter, the DPC has outlined a series of questions about the Abú system to the party that it says it wants answered.

These include an explanation of the legal basis for the processing of the information contained in the database.

"We can confirm that we have received correspondence from the Office of the Data Protection Commission," a Sinn Fein spokesperson said.

"We look forward to engaging with them."

It is understood that at this point, the DPC's inquiries are exploratory and aimed at establishing facts.

Reports about the system in the Irish Independent in recent days have prompted calls from Fine Gael for Sinn Féin to disclose more information about the issue, including where the information is stored and who has access to it.

Sinn Féin sources said the database is comprised of the electoral register and that it is hosted in the EU, and not in the US as had been claimed in some reports.