Decades of sex abuse cover-ups within the Catholic Church are intrinsically linked to the fact that so many cardinals, bishops and priests are gay, the author of a new book on homosexuality within the Vatican said on Wednesday.

Bishops are so terrified of being outed as gay that they have been resistant to reporting priests accused of raping and molesting children, said Frédéric Martel, the author of In the Closet of the Vatican.

The claims were made as victims of clerical sex abuse demanded a policy of zero tolerance from the Vatican and Pope Francis likened critics of the Church to “the devil”.

The book, which alleges that a majority of Catholic clergy are homosexual, will be published in several languages in 20 countries on Thursday.

It coincides with Pope Francis opening an unprecedented, four-day conference at the Vatican on how to combat the scourge of sex abuse.