Micheál Martin says "level three plus" is likely in January.
The Taoiseach says there's a very strong likelihood that pubs and restaurants will be closed for New Years.
His comments follows a recommendation from NPHET, which has also advised that the number of households allowed to mix be reduced after Christmas.
Health officials have warned that the virus is spreading faster than it anticipated after easing restrictions at the beginning of the month.
Micheál Martin believes it's likely the country will be in "level three plus" in January and says we can't ignore the potential impact celebrating Christmas will have on the virus.
''I said back in October we wanted to give people a meaningful Christmas, that will happen'', he said.
''And I think for mental well being purposes and just family's meeting that's important.
''I think they're looking at what happened at Thanksgiving in Canada, and in the United States when big days did have serious repercussions in terms of the spread of the virus, and we can't be blind to those either''.
CMO says we can't afford to celebrate Christmas and New Years.
Meanwhile, the Chief Medical Officer says we cannot to afford to celebrate both Christmas and New Years.
Dr Tony Holohan says he believes the duration of the easing of restrictions, from today until January 6th, needs to be shortened.
''That length of time is simply too long'', he said.
''Over the Christmas and New Year period people are coming together, particularly taking place in settings that facilitate bringing people together''.
''The use of alcohol in those kind of settings, and alcohol let's be honest is a particular challenge for us in this country, creates a particular challenge in maintaining social distancing and high standards of public health behaviour that are essential in the prevention of transmission of this infection''.
From today people are allowed to travel to any county in the country and mix with two other households.
You can learn more about what restrictions are in place, here.