There is a recent photo of Pope Francis doing the rounds on social media that shows him walking alone, without security people or a private secretary, across a Vatican courtyard. In the early days of his pontificate, it would have been seen as Francis breaking through the stuffy conventions of the Vatican: being his own man. Five years on, it is instead viewed as symbolic of Francis’s loneliness. Here is a man struggling to find allies or support from the Catholic faithful in his stalled efforts to reform the church and failing attempts to tackle the abuse crisis.

That crisis now threatens to engulf his papacy and do lasting damage to Francis’s own reputation. The scandal has grown from being, as the church once claimed, about a few bad apples, to a global disaster, revealing not only cover-ups by bishops of priests’ behaviour but accusations against archbishops and cardinals, the princes of the church. So bad is the situation that it has edged ever closer to the pope himself, with two of the members of his C9 group of cardinal advisers now tainted by abuse scandals. (It should be noted that the C9 members involved dispute the claims.)

In recent days the Catholic church has also been rocked by accusations against one of the most respected cardinals of recent times, the retired archbishop of Washington DC, Theodore McCarrick. The Vatican has ordered him to cease public ministry. McCarrick, 88, was a confidant of presidents and popes, including Francis.

Above all, there has been cultural resistance within the church over abuse

The scandals now lead to routine expressions of sorrow from the Vatican and other Catholic outposts. But this is not enough. Victims, Catholic laity, and indeed innocent clerics viewed as possible miscreants by a cynical public need action to be taken to at last root out the abusers, work out the causes and enact reforms.

This is not, of course, a contemporary problem of Francis’s own making. The vast majority of the cases coming to the fore are historical. The pope has inherited not only a backlog but a church which for decades was reluctant to act – and all too often run by a hierarchy keen to hide scandals, as the movie Spotlight, about the Boston paedophile priest scandal, so vividly portrayed.

The election of Francis in 2013 prompted hopes of a much-needed change in culture. He soon created an advisory commission on the protection of minors, appointing lay people such as British psychiatrist Lady Sheila Hollins and also victims. But the commission has foundered and the victims have quit, frustrated at lack of progress.

The pope has been up against an intransigent church bureaucracy. Vatican officials have proved unwilling to cooperate with the commission; nor has it been furnished with enough resources. But above all, there has been cultural resistance within the church over abuse. The clerical caste is one shaped by obedience and a deep fear of sullying the reputation of the church. The relationship of bishop and priest is a paternal one; if the priest errs, the bishop may focus on forgiveness of the miscreant rather than punishment of an abuser, while his greatest focus is on avoiding publicity. But the church is now reaping what it sowed: like long-festering sores, the suppressed scandals are erupting everywhere. The greatest of those involve accusations about members of the hierarchy themselves as abusers. Some remained hidden until now because pliant priests have been reluctant to “shop” their bishops, even when they themselves have been abused as young altar boys and seminarians.

Many critics also claim that celibacy is the cause of abuse in the Catholic church. But other institutions from the Church of England to the BBC and the Football Association have reeled from abuse scandals and have no such requirement. What the scandal does definitively show is that many who have advocated chasteness have shown contempt for it themselves.

If Francis is to get to grips with this scandal then he must act fast. A tribunal needs to be set up in Rome to deal only with abuse cases, run by expert investigators, and testimony needs to be heard. This is something the commission advised in 2015 but is yet to materialise.

Francis also needs to draw up a document – what’s called an apostolic constitution – on abuse that will outline the problem, examine the causes and state clearly how the church in four quarters of the globe will deal with the problem. There must be some leeway; the church operates across the world, including in totalitarian states where a fair criminal trial is unlikely for the accused. But some standards regarding inquiries and treatment of victims must surely be possible, as well as clear guidance on assessment of recruits to the priesthood. And the exit door for bishops needs to change: the church’s canon law says they can only retire when they reach 75 or for reasons of ill health. If they are guilty of wrongdoing, we don’t need the euphemism of them being in the sick bay.

In a few weeks’ time, Pope Francis has a golden opportunity to speak about abuse when he is due to visit Ireland, a country so stricken by abuse scandals that once-loyal Catholics are turning their back on the church. It took time for Francis to realise he had to do it, but in May he wrote a letter to the people of Chile decrying a culture of abuse and cover-up there. Now he needs to do the same for Ireland, and then return to Rome to get a grip on the scandal at last. We Catholics deserve this. Especially the children the church failed to protect.

• Catherine Pepinster is a former editor of The Tablet, and the author of The Keys and the Kingdom: the British and the Papacy from John Paul II to Francis