Altar wine is an essential part of the Eucharist, the ritual in which Catholics believe the body and blood of Jesus Christ is represented by the bread and wine. A priest drinks a small amount of the wine during the Mass.
Under proposed Irish legislation, the limit of 80 milligrams of alcohol per 100 millilitres of blood is expected to be tightened but no new level has yet been specified.
Because the ranks of the Catholic clergy are thinning out, priests, especially in rural areas, often drive to several churches on Sunday to say mass for congregations who have no resident clergy.
"You could be over the limit trying to travel between maybe two or three churches on a Sunday morning and coming back again," Father Brian D'Arcy told Reuters.
D'Arcy is a broadcaster and rector of the Passionist Monastery in Enniskillen, Northern Ireland, where similar changes have also been proposed.
He said wine prepared for use in services had to be consumed and throwing it away was blasphemous.
Irish media quoted another priest from western Ireland as saying he often took three services in a day.
"If I only took a mouthful of wine from the chalice at all three masses, I feel that this could put me over the legal limit for driving," the unnamed priest was quoted as saying.
"But if a call comes in that somebody is nearing death, I have no choice but drive to where that person is and give him or her their last rites."
Father Iggy O'Donovan from Drogheda, north of Dublin, said members of the congregation could always help finish the wine if too much was left over.
"The day that the celebration of the Eucharist becomes a defence for drunk-driving, I am afraid it beggars belief," he told RTE radio.