The Vatican has criticised sharply a 2005 book by a US theologian and nun on sexual ethics, where she defends gay rights and equal marriage.

The BBC reports that the Holy See’s Orthodoxy Office said that Sister Margaret Farley’s book, Just Love, posed ‘grave harm’ to the faithful, and that her ideas on masturbation, homosexuality, equal marriage and remarriage were in ‘direct contradiction’ to traditional Catholic teaching on sexual morality.

In addition, the Congregation for the Doctrine of the Faith has declared that her writings betrayed a ‘defective understanding of the objective nature of natural moral law.’

The Vatican has banned the use of the book by Catholic teachers, in a notification signed by the department head Cardinal William Levanda and approved by the Pope.

Sister Farley has defended her work, however, saying that the ideas they contain were entirely coherent with theological tradition. In her book, she writes that ‘same-sex oriented persons as well as their activities can and should be respected.’ Her book also argues for equal marriage as a means for reducing hatred against and stigmatisation of gay people.

Today’s statement by the Vatican however reaffirms its position that homosexual acts are ‘intrinsically disordered’ and ‘contrary to natural law.’ Marriage, it says, can only be the union between a man and a woman.

In a statement today, Sister Farley, who has eleven honorary degrees to her credit, and is an emeritus professor at Yale, said that she used a ‘criteria (sic) of justice’ in evaluating sexual morality. “The fact that Christians (and others) have achieved new knowledge and deeper understanding of human embodiment and sexuality seems to require that we at least examine the possibility of development in sexual ethics,” she said.

Recently, the Vatican has been highly critical of US nuns, moving so far as to denounce the Leadership Conference of Women Religious, whose members represent some 80% of 57,000 American nuns, as becoming ‘feminist’ and ‘politicised,’ promoting unorthodox ideas on sexual morality and challenging the authority of (male) bishops.