In the movie I Confess, Montgomery Clift plays a priest who refuses to break the secrecy of the confessional, even though his silence puts his own life on the line.

This 1953 film is considered the most Catholic of all Alfred Hitchcock’s work. The master of suspense was raised in the faith, and growing up in London attended the Salesian College in Battersea, and the Jesuit St Ignatius College in Stamford Hill, both establishments where he would have known many priests. After the film’s completion, the director mused that Catholics everywhere would instinctively understand the premise that a priest would risk his life for the sanctity of the confessional, while Protestants and non-believers would probably find the whole plot line ridiculous.

Hitchcock’s take seems apt today in the wake of the call from the royal commission into child sexual abuse in Australia, which has recommended the introduction of legislation that would criminalise priests who failed to report abuse disclosed to them in the confessional.

Denis Hart, the archbishop of Melbourne, responded by saying the sacredness of the confessional was above the law, and he would rather go to jail than report any sin he heard during the sacrament of penance.

His response would have come as no surprise to Hitchcock; and it comes as no surprise to me, another cradle Catholic. I would struggle to think of anyone raised in the Catholic church who would be surprised by it.

Child abuse is, it hardly needs to be said, a heinous and appalling crime that blights young lives, now and into the future. There is nothing that should not be done to prevent it. But the issue of confidentiality in the confessional is entirely separate, and it pertains to every terrible and unthinkable crime under the sun. To undermine it goes to the very heart of what all Christians believe, which is that no sin is so wicked that it cannot be forgiven by God.

In the Catholic church, the priest in effect “deputises” for God: he is a conduit, a mouthpiece if you like. He embodies, in that box, this fundamental Christian belief – that we can all be forgiven.

The logic of that belief is that the confessional is an entirely safe space – one of the only truly safe spaces in human life. So yes, child abuse is beyond contempt as a crime; but the child abuser, in common with any sinner – indeed, any human being – is forgivable and will always be forgivable, even if only by God. To deny that seems to me to be to deny our humanity. We must always separate the wrong from the wrongdoer, or what hope is there for redemption, and the crucial possibility of another chance, a better tomorrow, a reformed world?

We must always separate the wrong from the wrongdoer, or what hope is there for redemption

In the Catholic church, the recognition of our potential for redemption is symbolised by the confessional. And the promise the church makes to penitents is absolute: confession is a safe space where nothing is too terrible to be revealed and apologised for before God.

One of the essential requirements for confession is that a penitent is truly sorry, and genuinely intends not to commit their sin again. If a priest hears a confession of child abuse (or domestic violence, or murder), he is perfectly at liberty to strongly recommend that an individual seeks help, or talks to the authorities. A sincere penitent should be receptive to that suggestion. But – as Hitchcock understood – the buck stops in that box. It always has, and it always will.

• Joanna Moorhead writes about parenting and family issues