Frances Kissling, the former president of the liberal group Catholics for Choice, once told me that it was her ambition to discomfit the pope every single day. But that’s easier said than done. The Vatican has erected a fortress around itself that is so formidable that it seems impregnable.

Making any impact on that protective shield is almost impossible, but I had an opportunity to try recently at the United Nations Human Rights Council in Geneva. It was there, speaking as a representative of the International Humanist and Ethical Union, that I launched a fusillade that attempted to get the Catholic Church to face up to, and admit, its responsibilities in relation to child abuse.

Many had tried before. Earlier this year the Ryan Report in Ireland had revealed a devastating catalogue of abuse by priests that had been compounded by a systematic cover-up by the Church and repeated attempts to belittle victims and evade compensating them. Although this had dealt a severe blow to the Church in Ireland, the Vatican remained characteristically tight-lipped, waiting for this latest crisis to pass.

The Chamber at the UNHRC is huge and I was well back behind the international ranks of governmental and diplomatic representatives. The chair – whom I almost needed binoculars to see – called on me to start. The Holy See’s representative was listening more intently than usual, presumably because he had seen my statement of charges published by the UN and, probably by then, the text of my speech which had just been released.

As far as we are aware, no one else has ever berated the Holy See from the floor of a United Nations body.

I had very little time but a lot of complaints to make, so I jumped in without ceremony. I pointed out straight away that it was not the child abuse itself, but the Church’s handling of it that I was addressing. I complained about the 15 years of reports, mandatory under the UN Convention on the Rights of the Child (UNCRC), that the Holy See had failed to produce. Victims’ suffering had been compounded by being told they were liars, and if they had received any compensation it had been minimised. Senior clerics had been complicit in perpetuating the cycle of abuse by moving offending priests around like sinister chess pieces, and shielding them from civil authorities and likely criminal sanctions. The Church had done everything in its power, right to the very top, to cover up a massive problem that has been around for decades – some say centuries. I demanded full openness over abusers by the Church worldwide and for it to bring the reporting up to date.

The Holy See claims “its jurisdiction over a territory, known as the Vatican City State, serves solely to provide a basis for its autonomy and to guarantee the free exercise of its spiritual mission”. It is this enigmatic nation status that affords it the maximum influence with the minimum accountability – the very antithesis of secularism and a permanent “get out of jail free” card. The only law to which it is subject is international law and, as I showed at the UN, it breaks this with impunity. Clearly it has many friends in high places.

So, I concluded by calling on the international community to hold the Holy See to account – something that it has predictably, but shamefully, failed to do.

I was shocked to find that the Holy See’s accession to the UNCRC had been accepted despite it “reserving” (excluding) Vatican City, its entire geographical entity and we believe the very place to which all child abuse accusations are mandatorily sent.

My longer report, published by the UN, was much more specific and hard-hitting; it detailed, for example, five Articles of the Convention I accuse the Holy See of breaking, and demonstrated that the roots of the problem go to the very highest level of the Church.

From 1981 until his promotion, Benedict has been in charge of Church discipline. Bernard Law, the former Archbishop of Boston (the largest American diocese), was heavily implicated in massive cover-ups and life became too hot for him in the US despite the personal, and foolish, intervention of John Paul II. So, since 2004, he has been holed up in Rome where he also enjoys Benedict’s patronage. Despite the huge scandal that forced Law from office, he remains a cardinal and a member of the Pontifical Council of the Family. Revealingly, no bishop or cardinal has ever been laïcised (sacked) in connection with child abuse matters.

A few hours after I sat down, the Holy See exercised its Right of Reply, which was widely regarded as complacent, duplicitous and arrogant. It thought, for example, that the addition of just one paragraph on abuse by priests in this report that is 15 years overdue would suffice. The rebuttal then went on to claim, falsely, that US Protestants have an even worse record on child abuse. It said the abusers weren’t paedophiles (we never said they were), but homosexuals – Benedict’s new bogey men. The reply wilfully missed the point that sex – indeed physical or mental abuse of any kind – by anyone in authority against someone in their charge is an abuse of that authority on top of the wrongs of the act itself.

The rebuttal was an obvious attempt to deflect attention from the charges I had levelled at the Vatican by introducing other issues that had never been mentioned in the original speech. Most significantly, not one of my many charges did they even attempt to deny – because they couldn’t.

The Holy See soon realised that Archbishop Nuncio Tomasi – who had written the rebuttal – had made a spectacular misjudgement with his evasiveness and lack of compassion for the victims. No wonder this Right of Reply was conspicuous for its absence from the Vatican’s website. Its press officer told a newswire’s Vatican correspondent: “the Vatican had chosen not to publish it, in order not to ‘add gasoline to the fire’ on a volatile topic.”

The only other reaction from Rome was to describe my intervention as “a very hard and unjust attack”.

The media reaction, though, was far harder. American Public Radio, for example, covered the matter in a detailed article on its website which concluded: “let Archbishop Tomasi have the limelight and the microphone all to himself. It is hard to imagine what the Church could possibly do to look worse than it already did in the face of a global scandal that has cost it $2 billion in settlements in the United States alone. Hard to imagine ... and yet somehow, that’s precisely what it did.”

Neither Benedict, Tomasi nor their colleagues have yet realised just how much the Church’s previously unquestioned authority has been eroded. They need look no further than the 50 newspapers and major blogs in 15 countries around the world that covered this exchange, with hardly any disagreement with the stance I took. The Tablet even ran a lead editorial lambasting Tomasi.

I want to expunge the unspoken rule that the Holy See is above criticism and encourage the international community to take its responsibilities in this respect more seriously. The needs of children should have been the prime concern, rather than massaging the Vatican’s ego or indulging its unquenchable appetite for power.

Clearly, the Vatican has shot itself in the foot, and I am very happy to have given them the bullet with which to do it. The hundreds of thousands of victims of the Church’s cruelty deserve no less.