They say they have been subjected to "aggression, humiliation and spiritual manipulation" as a result of the "attitudes and ambitions" of Bishop Michael Olson.

It comes after Bishop Olson, the bishop of Fort Worth, claimed the head of the priory had broken her vow of chastity with a priest from outside the area.

In a statement this week, the Discalced Carmelite Nuns of Arlington denied the claims about their Mother Prioress.

The last few months have seen a battle between the nuns and Bishop Olson inside and outside court, featuring claims of spying, threats of excommunication and an intervention from the Vatican.

Who are the Discalced Carmelite Nuns of Arlington?

The saga centres around a group of nuns who live at the Monastery of the Most Holy Trinity in the city of Arlington, Texas.

They are part of the order of Discalced Carmelites, a Catholic order established in the 16th century.

Under Catholic canon law, their community is considered to be autonomous and nuns renounce family in pursuit of deeper connection with God.

By latest count there are thought to be around 11,500 Discalced Carmelite nuns spread out across the world.

What started the feud with Bishop Michael Olson?

It dates back to April this year when Bishop Olson, the diocese says, received a report that Reverend Mother Teresa Agnes Gerlach - the Mother Prioress - had violated her vow of chastity with a priest from outside the area.

"An ecclesiastical investigation into the report of the grave misconduct was initiated," the diocese said in a statement in May.

In response to the claims, the Arlington nuns filed a million-dollar lawsuit against Bishop Olson and the Catholic Diocese of Fort Worth.

In court documents obtained by NBC5 - Sky News's sister outlet - the nuns claimed Bishop Olson was overstepping his power by disciplining them and taking personal property from the monastery when they answer directly to the Pope and not the local diocese.

The lawsuit alleged that the Bishop took property, namely a computer, iPad, and mobile phone, from Reverend Mother Teresa Agnes Gerlach, and that after she replaced her confiscated phone her texts were monitored.

They accused the defendants of "spying" on the Sisters by accessing the phone.

District Court Judge Don Cosby ultimately ruled the civil court didn't have the jurisdiction to rule over a canonical dispute.

What have the Discalced Carmelite Nuns of Arlington said?

On 18 August, a statement released on behalf of Reverend Mother Teresa Agnes Gerlach and the chapter denied claims that had been made against them.

"In recent months our monastery in general and our Mother Prioress in particular have been subjected to unprecedented interference, intimidation, aggression, private and public humiliation and spiritual manipulation as the direct result of the attitudes and ambitions of the current Bishop of Fort Worth," they said.

It continued: "Our filial trust has been abused by the personal and public behaviours of a man who, in the pursuit of his unspecified personal ends, does not fear to shout at nuns or to humiliate them in private and in public when they protest that their rights have been ignored, who does not hesitate to violate their sacred enclosure through his officials, and whose actions in respect of personal property and privacy are more than seriously questionable."

In respect of the "calumnies" (false statements) that have been published, the nuns expressed "complete confidence in the personal and moral integrity of its Mother Prioress and in her leadership".

The blistering statement ended with the nuns announcing that they no longer recognise the authority of Bishop Olson and forbid him and his officials from setting foot on monastery property.

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What has Bishop Michael Olson said?

In a statement the following day, Bishop Olson said the rejection of his authority "hurt me as a friend".

He continued: "Thus, it is with deep sorrow that I must inform the faithful of the Diocese of Fort Worth, that Mother Teresa Agnes, thereby, may have incurred upon herself latae sententiae, excommunication."

Bishop Olson warned that the other nuns "depending on their complicity in Mother Teresa Agnes' publicly, scandalous and schismatic actions" could also have incurred excommunication.

"I stand ready to assist Mother Teresa Agnes on her path of reconciliation and healing," he added.

Previously, the bishop said that "baseless and false claims" have been made and caused "confusion".

In a video message on YouTube he claimed that the Mother Prioress had "admitted" breaking her vow of chastity and said any claims of "spying" on the sisters were "ludicrous".

An intervention from the Vatican?

The ongoing scandal has even reached the ears of senior Catholic figures in the Vatican.

At the end of May, the Vatican appointed Bishop Olson as the Pope's representative and apparently gave him "full governing powers" over the priory.

Another senior Catholic, however, has spoken out in support of the nuns.

In a statement published on the monastery's website, Archbishop Carlo Maria Vigano praised the "courageous resistance" of the Texas nuns.

Archbishop Vigano, best known for publicising two major Vatican scandals, even appeared to be critical of Pope Francis over the matter.

He added: "The Sisters of the Arlington Carmel have an example of heroic resistance against corrupt power in the martyrdom of the Carmelites of Compiegne, who knew how to face the guillotine in order not to submit to the constitutional oath of a revolutionary government.

"It will not be prelates without either dignity or faith who bend the bold resistance of souls in love with Christ."