The 91-year-old father of actor Mel Gibson has outed himself as a homophobe during a live phone-in on a US Christian radio station.

Hutton Gibson, who shares his famous son’s devout Catholicism, was a caller on the Political Cesspool Radio programme on the Liberty News Radio Network, where he was asked about the Church’s approach to issues such as homosexuality.

According to gossip website TMZ, Gibson senior reportedly let rip with a stream of invective, adding “Half of the people there in the Vatican are queer”.

When asked if he included Pope Benedict XVI among those people, he reportedly said, “I certainly do. Why else would he put up with this? He’s a slippery character”.

This is an unusal perspective on the pontiff, who has been a keen vocal opponent of gay rights and in particular, gay marriage.

The Political Cesspool show has long been a source of controversy in the States, having been accused in the past of stirring up anti-Semitic, nationalist and white supremacist views.