The nun had filed the complaint against the bishop two months ago.
A Kerala nun who has accused a Roman Catholic Bishop of raping her has petitioned the Vatican alleging that he is using "political and money power" to bury the case.
The nun alleges that by continuing in the position of Jalandhar diocese Bishop, Franco Mulakkal and his close associates "are using the wealth of the diocese" to divert the course of the police investigation.
"Seeking your urgent intervention in this case as the representative of the Holy See in India," she says in a letter to Giambattista Diquattro, Vatican's Apostolic Nuncio (a diplomatic mission) written on Saturday.
A group of nuns and others are protesting in Kerala against the delay in action against the bishop, who has been accused of rape and unnatural sex with the complainant multiple times between 2014 and 2016.
"They are arranging people to attack us and Bishop Franco is using his political power and money to get higher authorities of the investigation and the government to bury legal proceedings that I have filed against him," the nun charged in the letter, which surfaced in the media on Tuesday.
The nun alleges that the Bishop and his associates are buying support with the promise of land and other inducements.
The nun says she filed the complaint against the bishop two months ago, and even though the Special Investigation Team was convinced of the evidence, they were unable to arrest him because of his political and money power.
Copies of the letter have been sent to 21 others, including the Catholic Bishops Conference of India and the Delhi Metropolitan Archbishop.
"Being a religious sister who is denied justice from the congregation authority and from the church authority of Latin and Syro Malabar Churches, once again I implore your mercy on my situation," she says.
"I beg the Church authorities to kindly make a speedy enquiry about this case and remove Bishop Franco from his responsibilities as the spiritual leader of the diocese."
Protesters allege that top police officials are trying to sabotage the probe. With the police facing criticism, a senior official has said the bishop may be summoned to Kerala for interrogation.