Pope Francis has warned gender theory is part of a "global war" against traditional marriage and the family.

"You mentioned a great enemy of marriage: gender theory," the Pope said, in response to a question at a meeting of Catholics in the ex-Soviet republic of Georgia on Saturday

He continued: "Today, there is a global war out to destroy marriage.

"Not with weapons but with ideas... we have to defend ourselves from ideological colonisation."

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Gender theory is broadly the concept that while a person may be biologically male or female, they have the right to identify as male, female, both or neither.

The Pontiff has used the phrase "ideological colonisation" in the past to denounce what he says are attempts by rich countries to link development aid to the acceptance of social policies, such as allowing gay marriage and contraception.

"Marriage is the most beautiful thing that God has created," he said, adding that the bible says God created man and woman to become one flesh in apparent reference to homosexuality.

While he has been more accepting of homosexuality than his predecessors, Pope Francis opposes gay marriage.

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In the same answer, he also said the growing acceptance of divorce poses another threat to the family.

Last week, the Pope voiced his support for Mexicans campaigning against the legalisation of same-sex marriage.

He has previously warned that same-sex marriage threatens "the family" and could "disfigure God's plan for creation".