Powerful Catholic Church in Poland has declared war on "gender theory", saying it undermines the traditional family.
But critics say that is a tactic to shift attention away from a paedophile priest scandal.
The theory explores sexual orientation and the roles assigned by society to individuals based on their gender, but the Polish Church has borrowed the English word "gender" to refer to a range of issues including contraception, abortion and homosexuality.
While many say gender theory promotes tolerance and understanding towards gender equality and homosexuality, the Polish Church has branded it a mortal danger to families, child sexual orientation and humanity.
Polish bishops wrote a letter on the topic that was read out in every parish across the country over the Christmas holidays.
"This is a preventative offensive," sociologist Edmund Wnuk-Lipinski told AFP.
"The Church fears social change and it especially opposes gay marriage, something that's happening in other countries like France or certain states in the US."
Inspired by then pope Benedict XVI's remarks in late 2012 about the "falseness" of gender theory, the Polish campaign has taken on epic proportions and sparked a fierce, high-profile national debate.
Critics argue it is designed to shift focus from a recent string of paedophile priest scandals that rocked Poland, one of Europe's most Roman Catholic countries but whose loyalty to the Church is waning.
"Someone advised the Church to find a topic that would make people forget about the paedophile scandals that Polish media was fixated on these last few months," leading Polish religious affairs commentator Adam Szostkiewicz told AFP.
"Now not a day goes by that a bishop doesn't warn against gender," he said.
Allegations surfaced last year that two high-profile Polish priests had engaged in sex with boys.
Prosecutors began probes in September against 65-year-old archbishop Jozef Wesolowski, who served as a papal envoy in the Dominican Republic's capital Santo Domingo, and 36-year-old Wojciech Gil, who also served on the Caribbean island.
Poland's top cleric meanwhile provoked outrage when he suggested that parents shared the blame for paedophilia.
Archbishop Jozef Michalik later apologised for saying that paedophilia "manifests itself when a child is looking for love" and could be avoided "given a healthy relationship between parents".
According to feminist activist Kazimiera Szczuka, the war against gender is just the latest attempt by the Church to shift blame.
"By claiming that gender theory skews child sexual orientation, the Church wants people to think that it is indeed this theory that's responsible for sexual abuse, and not priests," she told AFP.
The Church letter to parishioners alleges that gender theory has "for the last several months been introduced without Poles' consent within various social institutions: education, health care, non-governmental organisations and cultural institutions".
The bishops cite Marxism, feminist movements and the sexual revolution as having inspired the theory, which they say is "contrary to the traditional view of man".
They warn that gender theory allows an individual to "freely define himself as a man or woman and choose his sexual orientation".
In certain parishes, an extreme version of the letter claimed that school sex education -- not yet a part of the Polish curriculum -- leads to "severe youth depravity".
The Church views the traditional definition of family headed by a man and a woman as the basis of society, according to Marcin Przeciszewski, head of Poland's KAI Catholic news agency.
He regrets the "unfortunate choice of words" of some Church members that "clouds the main message".
"The Church cannot agree to the idea of the interchangeability of the sexes. Sexual identity is accorded by nature, by God," he told AFP.
But some say the Church is misguided in demonising gender theory, since it is mainly a scientific concept and not tied to any particular ideology, according to expert Agnieszka Rajewicz-Kozlowska.
"In most official documents, the term 'gender' is linked to the idea of equality between men and women," said Rajewicz-Kozlowska, the government's deputy minister in charge of gender equality.
Yet, according to Szostkiewicz, the Church has turned "gender" into a grab bag and tossed everything into it: civil unions, gay marriage, abortion, in-vitro fertilisation, gender equality and sexual education.
He says the strategy has helped convince a portion of the population, thanks in large part to those who "only a couple months ago knew nothing about the term 'gender' and had no idea that it has been studied in Polish universities for 20 years".
Among the more extreme examples of the scorn heaped on gender theory, priest Dariusz Oko said: "Gender ideology is in some ways worse than Nazism and communism."
"It leads to the destruction of the nation" because it "destroys the family," he said.
This view has been echoed by Poland's political right, with a minor opposition party recently launching a committee against gender theory in parliament.
Committee members have assigned themselves the task of "protecting nursery school children against a sexualisation (introduced) under the guise of classes on gender equality" that were co-funded by the European Union and other international organisations.
Following warnings from Polish bishops and right-wing politicians, parents in many schools across the country have demanded that such classes be banned.