Catholic couples in Spain will undergo up to three years of marriage preparation under an initiative by their bishops to reverse the country's high rates of divorce.

The Spanish bishops launched Together on the Way ("Juntos en Camino"), a program to help couples to succeed in their vocation to marriage amid a divorce rate that sees about 40% of marriages collapse within five years and nearly 60% within 15 years.

The new course could last between two and three years; it replaces preparation courses that lasted between five and 20 hours.

Speaking at a news conference in Madrid mid-January, Bishop Mario Iceta Gavicagogeascoa of Bilbao said he did not believe previous courses were adequate.

"What can we do in five hours?" asked Bishop Iceta, president of the Spanish bishops' subcommission for family and the defense of life.

"To make a comparison, to be a priest you need to spend seven years in a seminary," he said, adding that it was not "sufficient" to prepare to be "a husband, a wife, a mother or a father" in less than a day.

He said that, as a parish priest, he would often bluntly tell couples that marriage preparation was not only an administrative process but a way of preventing the future collapse of their marriages.

The new course, the bishop continued, was a response to the requests of St John Paul II and Pope Francis to "accompany people who have discovered the vocation to marry" and to prepare them well for marriage.

He explained that while it was an obligation for the church to prepare couples for marriage, the course was not compulsory in its entirety and could be adapted to personal circumstances.

"Each diocese establishes the formation that is required for couples seeking matrimony," he said.

Dioceses must consider the provision of "adequate formation, while at the same time not dissuading young couples from the sacrament," the bishop added.

A statement posted on the website of the Spanish bishops' conference said the new approach to marriage preparation was collectively approved a meeting of the bishops in November.

It explained that the main objective of the course was to accompany couples in their own discernment of the vocation to marriage and in the choice of their true spouse.

The new course consists of 12 themes, including communication, conflict resolution, fidelity, the vocation to marriage and the beauty of sexuality.

The bishops envisaged that each of the themes would be studied over two or three sessions, usually two weeks apart.

Materials produced by the bishops for the course advise engaged couples who are having sexual intercourse to stop and wait until they are married, fortifying their chastity through sacraments of reconciliation and Communion.

They also warn couples of the dangers of pornography, saying it "commercializes and falsifies the beauty of the conjugal gift."

"It is addictive and causes damage to the addicted person, including conditioning their capacity for a healthy and stable relationship," the materials say.