Civil liberties groups say Welsh Assembly Government proposals for a "smart card" are a way of introducing identity cards "through the back door".
Commuters in London use the Oyster card, which is a smartcard
Ministers say the card aims to improve the way people use library and travel services.
But campaign group NO2ID said it would be the "thin edge of the wedge" towards a national ID card scheme.
Assembly government officials are looking at exactly how the smart card scheme would work.
Public Service Delivery Minister Andrew Davies said the card was a central part of the drive to improve public services.
However, Suw Charman, founder of the Open Rights group, which campaigns on digital rights, described the scheme as "pointless".
She told the BBC Wales programme CF99 on S4C: "I haven't seen an argument about what's wrong with the existing cards.
"Why do we need to put all this information on one smart card that's going to keep a log on what people do and where they go? It's treating people like criminals."
Mr Davies insisted the proposed smart card was not related to ID cards.
He told the programme: "It's just a way of using technology to access things like library cards, and make it easier to use those services."
Mr Davies said the sole purpose of the smart card was to improve the way the public used services.
He acknowledged that as the technology developed the scope of the smart card could expanded to include other services.
AMs have given the scheme a cautious welcome, but warned against allowing the card to carry too much information.
North Wales Liberal Democrat AM Eleanor Burnham expressed concern about the idea of smart cards holding personal data in the wake of incidents where UK Government departments have lost information on thousands of people.
Plaid Cymru AM Leanne Wood, who has vowed to go to jail rather than carry an ID card, also had reservations about the smart card.
She wanted reassurances that the card "would not become compulsory... or turn into a precursor of an ID card, because that would be a serious concern".