The Vatican has issued an unprecedented religious text co-written by Pope Francis and his predecessor Benedict XVI in which the two men restate their opposition to equal marriage.

Pope Francis paid tribute to Pope Emeritus Benedict XVI in the encyclical on Friday, saying that the ex-pontiff had “almost completed” the text before stepping down in February.

The 82-page text restates the Catholic Church’s position on marriage saying it should be a “stable union of man and woman.”

“This union is born of their love, as a sign and presence of God’s own love, and of the acknowledgment and acceptance of the goodness of sexual differentiation,” reads the text.

In keeping with his predecessor, Pope Francis has often used emotive language in order to state his opposition towards equality.

Three years ago as cardinal he warned that efforts to legalise equal marriage in Argentina would “confuse and deceive the children of God.”

In 2012, Benedict XVI, as Pope, warned that introducing equal marriage around the world would risk the future of humanity itself.

In his message for World Day of Peace 2013, he said same-sex marriage is unnatural and poses a threat to “justice and peace”.

Earlier on Friday, Pope Francis authorised a second miracle attributed to the late pontiff, John Paul II, Benedict XVI’s predecessor, clearing the way for him to become a saint, with a canonisation expected later this year.

In his 2005 book, ‘Memory and Identity’, Pope John Paul II attacked advances on gay rights including same-sex marriage writing: “It is legitimate and necessary to ask oneself if this [same-sex marriage] is not perhaps part of a new ideology of evil, perhaps more insidious and hidden, which attempts to pit human rights against the family and against man.”