An Irish university has been accused of heavy-handed censorship after it suspended one of the most influential lay Catholic groups in Ireland from its campus for distributing alleged homophobic material.

The National University of Ireland, in Galway (NUI Galway), suspended the Legion of Mary as a college society last week after the distribution of posters with the headline, "I'm a child of God. Don't call me gay."

Up to 70 complaints were made against The Courage Community, a Legion of Mary linked group responsible for the posters pasted up in the university's library.

The A4 posters offered those of "same sex attractions" to "develop an interior life of chastity … to move beyond the confines of the homosexual label to a more complete identity in Christ".

In response to the complaints, the NUI Galway said it was committed to protecting the liberty and equality of all students.

The university said it had reviewed the actions of the society in the context of the college's code of conduct and policies governing harassment. It said this led to the immediate suspension of the Legion of Mary, which is understood to have only a few members in its college society.

The societies chairperson at the university, Patrick O'Flaherty, said he had been contacted by a number of students who were upset or felt threatened by the content of the poster.

In a statement, the university said it would not condone the production and dissemination of any material by students that discriminated against other students. The Legion of Mary has since apologised for any hurt caused.

But one of the main organisations opposing censorship around the world criticised the university's decision to suspend the Catholic lay group's presence on the campus.

Index on Censorship's spokesman and senior writer at the group, Padraig Reidy, said: "While the view expressed in the flyer may seem archaic on a modern Irish university campus, it doesn't constitute intimidation nor threats. NUI Galway claims it is 'committed to protecting the liberty and equality of all students', but I don't think they've given any serious thought to the religious liberty or free speech of the Legion of Mary students."

The legion was once one of the most powerful Catholic lay movements in the Irish Republic. It was founded in Dublin on 7 September 1921 and now has a presence in 170 countries.

In its mission statement, the legion says it "sees as its priority the spiritual and social welfare of each individual". Its statement says: "The members participate in the life of the parish through visitation of families, the sick, both in their homes and in hospitals and through collaboration in every apostolic and missionary undertaking sponsored by the parish."

Compared with the secretive and elite institution Opus Dei, which has been accused of exercising covert influence in Irish life including within the medical profession and politics, the Legion of Mary remains a much more grassroots, openly activist, Catholic organisation.

A number of Irish Catholic lay organisations and pressure groups are gearing up to oppose next year's government-backed referendum, which, if passed, will grant full equality to gay couples and allow them to marry.