The Diocese of Galloway has released figures showing the number of priests has more than halved since 1990, with the fall in churchgoers nearly as steep.
Across the diocese, which covers most of south west Scotland, there is currently one priest for every two churches.
In 1990 it had 55 priests for 53 churches. There are now 23 priests for 43 churches.
A note to parishioners in Ayrshire, Dumfrieshire and Galloway states that the situation is "no longer sustainable" and calls for "changes in mindset, in expectation and in structures", an indication that many Catholic communities will soon see long-standing churches shut and congregations having to travel to their places of worship.
It comes on the back of years of low morale among clergy and parishioners since a bitter civil war in the diocese in the 1990s, when three priests succeeded in preventing the then bishop Maurice Taylor's bid to move them following a Vatican court case.
The current bishop, John Cunningham, has been ill for some time and is embroiled in a dispute with a priest who claims to have been abused by another member of the clergy.
Church officials said the move illustrated an increasing transparency, following the most turbulent years in its recent history.
The Archdiocese of Glasgow, home to Scotland's largest Catholic population, last week announced it was beginning consulting with all its 90-plus parishes in the run-up to Christmas in the context of changing populations, dwindling congregations and clergy numbers. Parishes are expected to close or merge as a result.
The document circulated across the diocese states: "Such changes however are not issues to be faced at some time in the future, but must be planned for and developed now."
At present, the number of those attending mass in the diocese is around 9200, down from nearly 18,200 in 1990. But while Catholic parishes are on average three times bigger than Church of Scotland parishes, South and East Ayrshire and Dumfries and Galloway have some of the highest national Kirk attendances.
One Ayrshire parishioner said: "We have been threatened with this for a decade but no-one has had the courage to do anything. But its sounds like its getting real. It's really a job for John Cunningham's successor but in the meantime parishes are left in limbo."
A Catholic Church spokesman said: "As with other dioceses Galloway must match provision with need. While Scotland's Catholic population has grown in recent years, that growth is not evenly spread across the country.
"For example in the Diocese of Aberdeen the Catholic population has almost doubled in the past six years but has fallen elsewhere. Such realities require careful pastoral planning including open communication with clergy and laity in exactly the way shown by the Diocese of Galloway."