Organisations representing the elderly have expressed concern over an admission that the Public Services Card is "mandatory" to access social protection services.
On Newstalk Breakfast earlier, Minister Regina Doherty claimed the card is not compulsory as "nobody is required by law" to have one.
But she said Government departments will refuse to provide citizens with the basic public services they are entitled to if they refuse to sign up.
Her comments came after a woman in her 70s was refused her State pension because she did not want to sign up for the card.
Justin Moran is head of advocacy at Age Action.
He said: "In January the department told us that one-in-four people with a travel pass did not have a Public Services Card.
"Even if this figure has improved, it still means tens of thousands of older people do not have a card.
"Earlier this week it was revealed a woman in her 70s had her pension cut off because she does not have a Public Services Card.
"We would be very concerned if this new requirement for the card leads to more older people losing their entitlements and we would urge the department to ensure no one is penalised because they do not have a Public Services Card."
'A huge step without asking the public first'
Fianna Fáil's spokesperson for social protection, Senator Catherine Ardagh, has said it is essential that the Oireachtas are given an opportunity to debate and consider the concerns.
Senator Ardagh said: "It is important to note that this card has been in operation for those who require Social Protection services since 2011.
"This is not the first time a national ID card system has been mooted.
"The use of biometric data being incorporated into the public services card in order to seemingly eliminate the possibility of fraud and to improve the efficiency of public services will bring personal rights into sharper focus.
Responding Minister Regina Doherty's comments, Green Party technology spokesperson Councillor Ossian Smyth said: "It is sinister that Fine Gael is now revealing that the real purpose of its mandatory National ID card scheme is to deny services to the public.
"The Government is bringing in mandatory identity cards for Irish citizens.
"This is a huge step to take without asking the public first - and the first way they are being used is to deny rights to citizens."
Social Protection response
In reponse, the Department of Social Protection said in a statement: "The Public Services Card (PSC) is precisely that, a card for accessing public services.
"It helps customers access a range of public services easily.
"The user’s identity is fully authenticated when it is issued so they do not have to give the same information to multiple organisations.
"It was first introduced in 2011 and was initially rolled out to people getting social welfare payments. It is now being rolled out to other public services."
The department adds: "The Public Service Card is a card for accessing public services only.
"It is a token which proves that a person has had their identity verified to a substantial level of assurance in accordance with the SAFE 2 standard.
"It is governed in that context by legislative provisions in the Social Welfare Consolidation Act 2005 (as amended), which limit its usage."
It says the card does not have "any of the typical characteristics of a national identity card", in that people are not required by law to provide it to a member of the police force at their request.