Elderly priests are being forced to work harder and longer well into their seventies as a way of dealing with a shortage of clergy.
A spokesman for the Association of Catholic Priests (ACP) has lashed out at the country's bishops accusing them of "elder abuse" for their treatment of the ageing religious.
Fr Brendan Hoban warned that pressure, both direct and indirect, to continue working is being put on priests who have a right to retire at 75.
The Co Mayo-based parish priest is one of over 30 signatories to a letter to Pope Francis by leaders of international Catholic reform groups imploring the Pontiff to do something about the trend of parish clustering or merging in Ireland and other countries.
"Priests are being spiritually manipulated and exploited and made to feel selfish unless they cooperate," he told the Irish Independent.
The merging of parishes has taken place in most dioceses in Ireland.
According to Fr Hoban, clustering places increased administrative and managerial responsibility on the shoulders of older priests trying to run mega parishes.
"Clustering, for some priests, has become a form of spiritual blackmail," he said.
The ACP leader, whose group represents over 1,000 Irish priests, described it as "a disrespectful, dishonest formula which allows bishops to pretend that the crisis can be dealt with".
The "reality is that no matter how you cluster parishes, 'clusters' will run out of priests within a decade or so. It's a mathematical certainty and the evidence is on the bishops' own website."
However, Bishop Francis Duffy of Ardagh and Clonmacnoise said in his experience no priest was asked to stay on beyond 75, but that some priests did ask to remain in ministry for longer.
Speaking to the Irish Independent in Longford, he said he would meet any priest in his diocese who was approaching 75 and tell him, "You have a right to retire and that has to be respected."
Bishop Duffy said he was "certainly concerned" that more was being expected of a smaller and older cohort of priests.
"My view is that 75 is the retirement age and if a person wants to stay on after 75, it is looked at a year at a time and only if a person wishes - I would never ask someone to stay on."
He said the issue of a declining number of priests was being discussed by the bishops and he questioned what the alternative to clustering parishes was.
"This is an issue that is being looked at the local level in dioceses. Parish pastoral councils are aware of the problem," he said of the decline in priest numbers and he added that he thought parish pastoral councils would have more decision-making in the future.
Another Irish signatory to the letter, Fr Tony Flannery, said that while clustering in Ireland at the moment usually involves up to four parishes and one or two priests, in France it could involve up to 10 parishes with just one priest. He warned that within 10 years that was coming down the line for the Irish church.
The letter warns Pope Francis that "bishops increasingly respond to the priest shortage by merging active and vibrant parishes into anonymous and unmanageable superstructures" where personal contact between people and priests is lost, leaving the faithful "alienated, unsettled and insecure".
In turn, priests are increasingly focused on administration instead of the community.
According to Fr Flannery, the current model of parish councils needs to be radically revised away from a consulting body to a decision-making one.