It is a mystery that would perplex Sister Fidelma or Father Brown – the continued exile and silence of three popular clergymen from a prestigious Catholic institution preparing for a visit from the pope.

The disappearance last May of Father Philip Cleevely, Father Dermot Fenlon and Brother Lewis Berry from the Birmingham Oratory has puzzled and angered parishioners, who want to know why the men have been dispatched to monasteries around the world, and are campaigning for their reinstatement.

It has led to accusations that they are paying the price for seeking help over the "intense but physically chaste relationship" between a young man and the head of the Oratory, Father Paul Chavasse.

Crime writer and historian Ruth Dudley Edwards, a lifelong friend of Fenlon, has taken up the cause of the "Birmingham Three" in Standpoint magazine.

In her latest article, she says the Vatican investigation into life at the oratory, sparked by the controversial friendship, has "blighted the lives" of the three men, and she condemned the wall of silence surrounding the inquiry and the exile.

Fenlon, now in the US, has found his reputation "in tatters along with that of the oratory", she said.

The lack of explanation from the Vatican team led outsiders to speculate about the reasons the trio were exiled.

Dudley Edwards said: "Has no one grasped from the one inference being taken from this mess is that the Birmingham Three are being punished for being whistleblowers?

"Has the church learned nothing from the scandals and the disastrous effects of a policy of silence and concealment?"

The widely reported unease casts a cloud over the papal visit to the oratory on 19 September.

Benedict XVI is due to pray there on the fourth and final day of his visit to the UK, following the beatification ceremony of Cardinal Henry Newman, who founded the oratory and is the principal reason for the pope coming to Britain.

Fenlon, a former Cambridge don, was a Newman scholar.

"The beatification and the visit to the oratory by the pope would have been the most joyful event of his life," wrote Edwards.

Jack Valero, spokesman for the oratory, said last weekend that "very serious things were going on" inside the oratory. Valero told BBC Sunday Sequence the men had been ordered to stay away because of disciplinary matters such as "pride, anger, disobedience, disunity, nastiness, dissension, the breakdown of charity".

The "very existence" of the 150-year-old community was under threat, he said.

Valero has written for this week's Catholic Herald and says the protests, which are based on "bizarre conspiracy theories", are harming the church.

"The spectacle is pitiful. The oratory hates it as much as the media loves it."