OMAHA, Nebraska — The Omaha Archdiocese has severed ties with a Jesuit university’s family centre after two researchers urged the church to allow unmarried couples to live together and have sex and children as long as they are engaged.The Creighton University researchers’ essay, published in the June issue of US Catholic magazine, said that more unmarried Catholic couples are living together today, and that they doubt the claim that the couples are living in sin.

“It would appear closer to the truth that they are growing, perhaps slowly but nonetheless surely, into grace,” Michael Lawler and Gail Risch wrote.

The essay prompted a letter to the editor from Omaha Archbishop Elden Curtiss. The June 5 letter, a copy of which was provided to The Associated Press by the archdiocese, aimed to discredit the researchers as Catholic theologians and dissociated the university’s Centre for Marriage and Family from the archdiocese.

“The teaching of the Catholic Church about fornication is clear and unambiguous; it is always objectively a serious sin,” Curtiss wrote.

Curtiss wrote separate letters to the authors and Creighton’s president, Rev. John Schlegel, said the Rev. Joseph Taphorn, chancellor of the archdiocese.

Taphorn did not know of any collaborations that were cancelled because of Curtiss’ decision, but said the archdiocese had worked with the university’s centre on several projects in the past. One project was designed to help couples assess their religious beliefs and bond from them.

“We will no longer be cooperating with them on future projects because there’s obviously a big theological difference,” Taphorn said.

A spokeswoman for the US Conference of Catholic Bishops said the proposal was an appalling attempt to gain the benefits of marriage without getting married.

“It’s better to help young people prepare for marriage and better to help them to make a lifelong commitment — which marriage is — than to have what sounds like some kind of quasi-marriage,” Sister Mary Ann Walsh said Thursday.

Lawler and Risch wrote that between the 12th and 16th centuries, the Catholic Church allowed couples to have sex once they were betrothed. That changed under the Council of Trent, but many modern Catholic couples have reverted to living together and having sex before their weddings, the authors wrote.

“Catholics who believe that all premarital sex is wrong believe that the ritual requirement of a wedding has always been the norm in the Catholic tradition. It has not,” the authors wrote.

Lawler is the director of Creighton’s Center for Marriage and Family and a professor emeritus of Catholic theology. Risch is a researcher for the centre.