Pupils could be denied a place at Catholic secondary schools unless they can prove they were baptised, under plans being considered by a Scottish local authority.
Children starting high school in East Renfrewshire could be asked to provide a Catholic baptismal certificate if they are moving to a Catholic secondary school in their catchment area which is oversubscribed.
Officials at East Renfrewshire Council put forward the plan prioritising places in St Ninian's High School - one of the top state schools in Scotland - and St Luke's High School for pupils who can prove they are baptised Catholics, to deal with the rising number of pupils at denominational schools in the east of the region.
Fiona Morrison, the council's head of education services, said in a report set to go before councillors on Thursday that families of any faith or none would be able to apply for enrolment at a Catholic school, but where they are oversubscribed by catchment pupils, "priority be given to baptised Catholic children" and non-Catholics would be sent to their local non-denominational school.
She added the proposal would allow the council to "plan more effectively school provision, provide sufficient places for its resident population and prioritise places for baptised Roman Catholic children in Roman Catholic schools".
If councillors agree, a public consultation will be launched on the proposals, which are not subject to ministerial call-in and will be brought in next January.
But Jim Swift, a Scottish Conservative councillor in East Renfrewshire, said the "worrying" state of affairs could have been avoided.
He said: "We have repeatedly warned the council that because of an increasing Catholic population, more denominational school places will be required.
"It has had several opportunities to get this right, and each time it has messed up.
"Labour and the SNP haven't listened, and now children in East Renfrewshire risk missing out on being educated at one of Scotland's best state schools unless they can produce a baptismal certificate.
"Across Scotland, many non-denominational pupils are happily taught in denominational schools, but now that's in jeopardy because both Labour and the SNP failed to heed the warnings."
The council's education director, Mhairi Shaw, said the education department carries out annual reviews to ensure capacity and due to increased demand, has increased teacher numbers, created additional accommodation and is investing £77.6m (€89.8m) over the next three years in extra facilities.
But she said that despite these steps, the council may not meet demand for Catholic school places in future.
She said: "We also know that we have space in our very high performing non-denominational schools in the east of the council area and as such we must seek to use all available capacity across our full school estate to achieve a fair and equitable solution.
"As more families want a place at Roman Catholic school for their children, it is essential that we either create more capacity for Roman Catholic education or change admissions arrangements for our existing schools."
Council leader Jim Fletcher said: "The Education Committee will consider the proposal to consult on these proposed new arrangements later this week.
"It must be stressed that the council is always in listening mode and takes on board all views to ensure that we arrive at decisions which provide the best possible services and standards for our residents."