Mary McAleese believes while the Vatican is losing its argument on its teachings, some youngsters in Catholic schools are left battling an internal conflict.
She said the numbers of young men who have died by suicide in Ireland is galling, with gay men one of the most at-risk groups.
“They are the victims, one, of homophobic bullying; they are also frankly highly conflicted,” said Mrs McAleese, who is studying canon law in Rome after her 14-year term ended in November.
She said the vast majority of children in Ireland went to Catholic schools, where they would have heard the Church’s attitude to homosexuality.
“They will have heard words like ‘disorder’, they may have heard the word ‘evil’ used in relation to homosexual practice,” said Mrs McAleese.
“And when they make the discovery, and it is a discovery and not a decision, when they make the discovery they are gay when they are 14, 15, and 16, an internal conflict of absolutely appalling proportions opens up.
“They may very well have heard their mothers, their fathers, their uncles, aunts, friends use dreadful language in relation to homosexuality and now they are driven into a space that is dark and bleak.”
She warned that with more debate, and greater research, the Catholic Church “is going to become increasingly isolated in its attitude to homosexuality” and gay people’s civil and human rights.
Her comments were strongly welcomed by the Gay and Lesbian Equality Network.
Odhrán Allen, director of mental health with GLEN, said: “We know from Irish research that the most common age to know you are gay is 12 but you don’t tell the first person until you are 17. This shows that for most young gay people there is a period of five years of isolation and fear of telling others before coming out.”
The former president met the Papal Nuncio Charles Brown, who represents Pope Benedict in Ireland, shortly after Easter to draw his attention to the issue.
But she fears the issue will not be tackled until the “omerta” or code of silence is broken.
She said the child abuse scandals have left “a massive hallowing out of trust” in the Church’s Episcopal leadership, but she believes it lost its grip on society years before as it insisted on obedience in a world where people were becoming increasingly educated and had access to other opinion.
Mrs McAleese, who has published a book, Quo Vadis: Collegiality In The Code Of Canon Law, also criticised the Church for not drawing on the views and anxieties expressed by its faithful.