SINN Féin last night denied it is "microtargeting" people using data collected from Facebook and the electoral register.
Eoin Ó Broin said the party's system of using public information about voters is "fully compliant" with the law.
It comes after reports Sinn Féin's internal database Abú gave party members access to a database which included names, addresses and predicted voting intentions of millions of voters.
The Republic's Data Protection Commissioner (DPC) has sought information about how the party uses its database and information collected from social media.
Commissioner Helen Dixon wrote to Sinn Féin seeking confirmation about its Abu system and whether it is GDPR compliant.
Mr Ó Broin said the party had provided full responses to all the questions.
"Our view is we're fully compliant with the Data Protection Act of 2018," he added.
"What we do with the electoral register is what any professional party does, we use the register to target our voters, and to ensure we get our vote out on election day - that is legally permissible under the Data Protection Act.
"We've responded to the Data Protection Commissioner, and if she has any concerns or if she has any suggested improvements to our system, of course we'll be glad to take those on board.
"We have to comply with the law and we believe we are fully compliant with the law, and the Data Protection Commissioner has asked us a series of questions and we've answered those.
"Then we'll all listen very carefully to what she has to say.
"I'm sure we'd be willing to share that with (the media) so you can have full sight of that."
However, it remains unclear if the database extends to Northern Ireland.
Sinn Féin has not responded to queries about whether its the database also holds information about voters in Northern Ireland elections.
Mr Ó Broin last night also refused to confirm which country within the European Union the database is kept.
"We don't have to say what country within the European Union it is but it has to be stored within the European Union," he added.
He said the system used "isn't something new".
"This is a professional way of going about elections, and any information that we have is fully consistent with the Data Protection Act of 2018, and so it should be," he added.
"We don't pay anything for the system, we don't charge anybody for the system.
"It's an electoral register system, a digital database that we use just like we used to use pen and paper before we had access to digital technology.
"What we use the electoral register for is what every political party knows their job is, which is to engage with the electorate, target your vote and get them out."
He added: "There are our claims that we are data mining from Facebook. It is not true.
"Any information I get from anybody on Facebook, they give it to me consensually - I asked him for it, they provide it - and I use that data for the purposes it's provided, as the law requires."
