The Catholic bishops have effectively blocked the use of a religious textbook in primary schools that was not produced by their own publishing house, Veritas.
Bishops have written to Catholic schools in their areas advising that only two titles, 'Grow in Love' and 'Alive-O', both produced by Veritas, are currently approved for use in their classrooms.
The letters arrived soon after the appearance of a rival offering for third to fifth classes, 'Friends in Faith', by educational publishers, CJ Fallon, whose representatives started promoting the book in schools in February.
Veritas company accounts show that it is depending on the 'Grow in Love' series - which is being phased in to replace 'Alive-O' - to help restore its financial fortunes, after some difficult years.
In his letter to principals, the Bishop of Limerick, Dr Brendan Leahy, who is president of Veritas, states that at this time 'Grow in Love' is the only programme approved for religious education and sacramental preparation in Catholic primary schools, while 'Alive-O' is also approved for use in the senior classes.
A similar letter from the education secretariat of the Dublin Archdiocese notes that it is the time of year when booklists are being prepared and that it is "delighted to confirm that 'Grow in Love' will be available for 3rd and 4th classes this September".
In response to a query from the Irish Independent, a spokesperson for the bishops said that in 2013 a review process was put in place to ensure conformity both with the curriculum and with Catholic doctrine of any religious education materials.
The spokesperson said that a number of individuals and publishing companies had engaged with this process, including Veritas, which had presented 'Grow in Love', but that CJ Fallon had not yet submitted any materials.
Veritas has enjoyed a monopoly in the provision of religious textbooks for primary schools, but the publication by the bishops, in 2015, of the first ever guidelines for a religion curriculum was seen to open up opportunities for other publishers.
CJ Fallon would not comment on recent developments, but the company's promotional material for 'Friends and Faith' states that the programme is in line with the curriculum guidelines which were published in 2015.
The National Council for Curriculum and Assessment sets down the curriculum guidelines for other subjects, and does not review the materials developed by publishers.
Legal sources said that the move by the Bishops could be deemed to be anti-competitive and a breach of legislation relating to the abuse of a dominant position.
Veritas has experienced considerable financial challenges in recent years, with a net loss of €1.8m in 2014, including an impairment charge of €1.1m, based on the drop in value of a warehouse in Ballycoolin, Co Dublin, purchased in 2006.