Indoor dining should not resume until September, according to People Before Profit TD Gino Kenny.
He was speaking as the Government finalises plans to reopen indoor dining in pubs and restaurants.
A reopening date is set to be decided later today, with ministers saying it will happen no later than July 26th.
However, indoor dining will be limited to people who are fully vaccinated or who have recovered from COVID-19.
Unvaccinated children will also be allowed to dine indoors once they are accompanied by a guardian.
The Oireachtas will need to pass legislation around the new rules ahead of the planned reopening.
Representatives from the hospitality sector will also meet with Government officials today to discuss how the rules will be enforced.
While industry groups have welcomed the opportunity to reopen, some opposition politicians have raised concerns about the plans.
Deputy Kenny - who is also a member of the Oireachtas Health Committee - told Newstalk Breakfast there are concerns around the new rules will work.
He said: "As a member of the health committee, we’re asking officials to outline the workability of the legislation.
“The essence is it’s discriminatory in relation to those who are unvaccinated. Those that are [working] in the hospitality sector... [there] are a lot of people that would be under 35.
“There are also concerns around a person’s medical information, and how this will work when it’s rolled out.”
He said the alternative is that indoor hospitality doesn’t open until September - something he'd personally support.
He said: “Everybody wants to get back to normal, and the hospitality industry has taken a terrible toll over the last 16-17 months. But you look at what’s happening in Britain, and they’re four-six weeks ahead of us… they’ll have up to 100,000 cases a day by the first week of August.
“That’s going to happen in Ireland, 100%, once you open indoor hospitality.
“The gains we’ve made over the last six or seven months… are we going to risk all that in the next six or seven weeks?"
Deputy Kenny acknowledged there will likely be fewer COVID-19 related deaths and hospitalisations in a fourth wave, given most vulnerable people are now fully vaccinated.
However, he said there's still likely to be an “enormous spike” in cases.
He noted that the vast majority of adults are set to be fully vaccinated by September - a situation that would allow reopening to proceed in a safer fashion.
