The Firework hitmaker was in negotiations with the Archdiocese of Los Angeles to buy the property formerly occupied by the Sisters of the Immaculate Heart of Mary in Los Feliz, but two ex-residents, Sisters Rita Callahan and Catherine Rose Holzman, objected.

They claimed it was their right to sell the eight-acre estate and they had already struck a deal with restaurateur Dana Hollister, who has moved in.

However, officials for the archdiocese stepped up the fight on Friday (24Jul15), when they filed new court papers seeking to have the agreement nullified amid allegations suggesting Hollister has taken advantage of the ageing sisters.

Documents filed in Los Angeles Superior Court accuse Hollister of paying just $44,000 (£27,500) of the property's $10 million (£6.25 million) price tag to date, stating: "The balance of the $10 million purchase price was reflected in her $9.9 million, non-recourse promissory note that did not require her to pay anything until July 1, 2018."

The attorneys add, "The transaction should be declared void as a product of elder abuse. It appears that it was ideal for Hollister, but terrible for the sisters and the institute."

Hollister has yet to respond to the accusations.

Judge Robert H. O'Brien is slated to decide who is the rightful seller of the convent at a hearing on Thursday (30Jul15).

The archdiocese planned to sell the plot to Perry in a deal worth $14.5 million (£9 million), which included a contract for the singer to provide an alternative property for the house of prayer, worth $4.5 million (£2.8 million), according to Patch.com.