The Association of Catholic Priests said the vocations crisis has become so critical that the day is looming when there won't be enough priests available in some parishes to conduct single funeral and wedding Masses.
The body, which represents over 1,000 Irish priests, issued the warnings on the eve of its annual general meeting on Wednesday.
Fr. Brendan Hoban, a founder of the ACP, said he believed the Catholic hierarchy now had little choice but to implement radical new changes to save hundreds of parishes from closing across the country.
The Co. Mayo-based priest said: "Unless the Bishops make changes, we're facing a catastrophic situation in the next 10 to 20 years because there simply won't be enough priests to supply Mass to our people. And if you haven't got Mass, then you no longer have a Church.
"The average age of a priest is 65 and their numbers are dwindling all the time. If you look at the Dublin diocese where there are 199 parishes, there is just one priest under the age of 40.
"In my own diocese of Killala there are 30 priests in 22 parishes, but we estimate that the way things stand there will be just seven in 15 years' time.
"The reality is that there are not sufficient male celibate vocations to keep our parishes alive. This year just 13 new seminarians have started at Maynooth – that's the future for the 26 dioceses of this country. When I started as a student in Maynooth in the early 70s there were 84 students in my class and well over 100 in the year above me."
The ACP has called on Catholic leaders to implement three proposals which they believe will save the future of the Church in Ireland – to ordain married men, to invite back priests who'd left the priesthood previously to get married and to ordain women to the diaconate.
And Fr. Hoban said he feels confident that these measures will be implemented – because there is now "no alternative."
He continued: "There is a civil war at the moment in the Church here between those who want change and those who don't.
"The Bishops are by nature very conservative, but they no longer have an alternative because the way things stand our priests are getting old, retiring and dying and very, very few new ones are getting ordained. If parishes start closing across the country because new measures weren't taken, there will be a big revolt from the people."
As it is, most dioceses across the country have had to resort to clustering in the short-term to compensate for decreasing priest numbers, whereby a number of parishes are amalgamated into a larger unit or cluster.
Fr. Hoban added: "One of the main functions of a priest is to say Mass. But we're facing a situation where there won't be priests available in some parishes for funerals, weddings or baptisms.
"That means there's a very real prospect of priests having to marry several couples at the same time. We could even be looking at having funeral Masses where there are up to ten coffins in the church at the same time."
The theme of Wednesday's AGM, at the Hodson Bay Hotel in Athlone, Co. Westmeath, is 'The vocations crisis: Will clustering work?'