Danny Healy-Rae says people should be allowed to drive after drinking a pint-and-a-half of beer.
The Kerry TD was reacting to claims that 11% of fatal crashes involving alcohol take place between 7am and 11am.
He says he does not believe three glasses of beer impairs a driver:
He said: "We need to get clarity as to what level of milligrammes (Shane Ross) is talking about.
"The pint and a half pint, or three little glasses, I firmly believe and still believe that this will not have an adverse effect on people's ability to drive.
"They certainly would not cause an accident."
Transport Minister Shane Ross had said: "Drivers need to be aware that they may not be safe to drive the morning after a night out, as they may still have alcohol in their system.
"As such, it is critical that drivers take measures to ensure their safety and the safety of others and this means leaving the car at home and making alternative arrangements for the morning after if they need to get somewhere."
The Road Safety Authority (RSA) and An Garda Síochána have launched a public information campaign to educate drivers about the dangers of driving the morning after drinking alcohol.
The RSA analysed An Garda Síochána Forensic Collision Investigation reports for fatal collisions that occurred on Irish roads between 2008 and 2012.
Specifically, they looked at alcohol-related crashes the morning after and found that 11% of the 222 fatal collisions in which a driver had consumed alcohol occurred during the early hours of the morning.
The new campaign includes two new radio advertisements and will be broadcast on all national and regional radio stations over the next three weeks.