The head of the Irish Council for Civil Liberties (ICCL) has suggested vaccination certificates could see vaccines mandatory by default.
It comes amid reports the Government is considering such proposals for vaccinated people to attend concerts, matches and restaurants.
While the European Union is working on a similar model to allow for international travel.
Liam Herrick, executive director of the ICCL, told Pat Kenny trying to apply this on a smaller, country-wide scale is problematic.
"Going from that to a policy of discrimination in terms of access to goods and services more generally - which would involve things like hairdressers or pubs or restaurants - asking people questions about their personal health status, controlling that data and effectively in an Irish context discriminating against huge sections of the population based on age and health status adds a whole layer of legal and rights issues".
He added that while he understands businesses want to open again, such vaccine certs could hurt the vaccine programme.
"If you go down the road of excluding people from services - and indeed from employment - on the basis of whether they've had a vaccine, it really undermines the principle of our vaccine programme which is one of voluntariness and consent.
"It's effectively making vaccines mandatory by the back door".
He said any such movement towards that may actually be counterproductive.
"Anything that would try to introduce a level of compulsion could have a counterproductive effect of actually feeding into that anti-vaccine movement and the skepticism of the vaccine programme".
And he said a vaccine is not yet proven to offer protection to others.
"You can see the appeal in theory, but the details.... in practice are a lot more complicated.
"From a starting point, the WHO itself has opposed the idea of states using vaccine certificate systems in terms of access to travel or goods and services.
"The reason it has is because, from its point of view, having had the vaccine is not equal to being safe.
"The question of people who've had the vaccine being able to transmit the disease is unproven at this stage.
"There's clearly evidence in favour of it, but it's not conclusive."
'Inevitably a two-tier system'
Dr Chris Luke is a consultant in emergency medicine in Cork. He said while the issue is controversial, he believes it will work itself out.
"It comes back to self-interest - without a doubt there's going to be huge controversy, and inevitably in life there's going to be a two-tier system.
"I was reading yesterday about the Branson cruisers - there are huge new cruise ships to be launched, that are mainly aimed at the 18 to 32 market.
"I gather the businesses are aimed at people who are very intent to have vaccination, that the requirement for these is to have a vaccine cert to get onboard.
"And I think we're going to see a lot of that: people who have the vaccine will take advantage."
But Dr Luke said this could see younger people particularly affected.
"You already highlighted the one big question, which is that young people will be particularly denied access to venues like clubs, pubs and whatever because they will be the last cohort to be vaccinated.
"So unfortunately we are going to be inflicted with controversy over this for the next few months, but I think it'll work itself out".