The curfew on the hospitality sector from Sunday will see people move from pubs to house parties, the Vintners' Federation of Ireland (VFI) says.
It comes as new restrictions will see all restaurants and bars close at 8.00pm.
For earlier indoor events, attendance will be limited to 50% of venue capacity or 1,000 people - whichever is lower.
The VFI says this is "the final gut punch" for the sector.
Its president Paul Moynihan told The Hard Shoulder this will take people to unregulated house parties.
"We're going to close down at 8 o'clock - you're going to see house parties, you're going to see shed parties.
"People have to get out and socialise, that's what they're going to do.
"Doing it in a safe environment, I think, is a lot better than doing it in house parties.
"I think that's what's going to happen now: we're going to put people in house parties up and down the country at 8 o'clock".
'We're in trouble'
And he says the industry is 'barely viable' as it is.
"I think 5 o'clock or 8 o'clock, it's not much difference to us. The vast majority of our trade is done later than that.
"And I think there's publicans - and their staff - up and down the country tonight, they're very, very worried.
"Where's the money going to come from to pay their mortgage, maybe, next month.
"The devil's going to be in the detail of what supports are going to come from Government to help us through this period.
"Villages up and down the country, the vast majority of pubs will only open at 5 in the evening.
"So to be open from 5 to 8, it's not viable - it's barely viable as we speak.
"We're limited to capacity with the lack of bar and the spacing out of furniture.
"We've had no Christmas parties, all parties have been cancelled up and down the country.
"The Christmas period is there to carry us through January and February, that's what pays the bill, so we're in trouble."
'Whole pandemic has been mismanaged'
While chef JP McMahon says the restaurant sector is 'effectively being closed'.
"I don't think we're in a much better place, I think we're in exactly the same place - except we're vaccinated and boostered.
"We're effectively being closed... does [the Taoiseach] mean at 8 o'clock the restaurant has to be empty?
"If that's the case I don't know how we can run a business like that.
"I'm very disappointed, I think the industry's being scapegoated again."
He says they Government has not taken enough action in schools and hospitals to contain the virus.
"And I think, again, the anti-alcohol anti-hospitality agenda is there to be seen".
He believes more could have been done, and that Omicron has not been shown to be more deadly.
"The data is not there to show that it is more deadly, it is more transmissible and they are pre-empting.
"But there are many, many more things - the schools will remain open.
"The whole pandemic has been mismanaged in Ireland, and I think what will happen is we will open on the 30th of January and then another strain will come and then we'll get closed again.
"The Government has to come up with some sort of plan within COVID to help us survive.
"We're haemoraging staff, we're haemoraging people - people are leaving, people are going home to their own countries."
He says Ireland is consistently taking the most drastic approach.
"We are certainly not the only country in Europe that are doing this, there are one or two other countries that are suggesting curfews.
"But most of them are not: we have to look at Europe, we have to look at our neighbours - and we are in a better position than England and our neighbours.
"But we are taking the most drastic line, and I don't think that's the best for our industry or even for our mental health."
And Mr McMahon says this is very late in the day.
"I have €1,000 worth of fish on order now that I have to either accept or cancel, and I'm sure that's just one example.
"It's very late, it's Sunday, there is no notice at all for this. This demonstrates that the Government do not understand the industry.
"If it was 10 o'clock - what is the difference in two hours scientifically? I don't know".