Indian Catholic sisters have broken ranks with the church by openly protesting in the streets of the Keralan state capital against a bishop accused of raping a nun.

The demonstrations started on Saturday and continued throughout the weekend in Thiruvananthapuram, fuelled by an incendiary press conference in which a politician questioned the account of the bishops’s alleged victim, a 46-year-old nun, and described her as a prostitute.

The nun lodged a complaint against bishop Franco Mullackal on 27 June this year accusing the clergyman of sexually assaulting her over a period of two years starting in May 2014.

She made the complaint only after Mullackal went to the police claiming the alleged victim and five other nuns were harassing and blackmailing him. He denies the rape accusations and says the alleged victim has a vendetta against him.

The case has exposed deep ruptures inside Kerala’s Roman Catholic church, whose adherents numbered close to 1 million according to the most recent census in 2011. The southern state has one of the largest Christian populations in India and one of the oldest in the world.

Former nuns have previously raised allegations of sexual exploitation by priests and other male clergy in the state’s church but the latest case has prompted unprecedented publicity and calls for investigation.

Five nuns joined street protests at the weekend organised by Catholic reform groups claiming the police were dragging their heels in the case. “The church has not given us justice,” one of the nuns, Sister Anupama MJ, told the Times of India. “Neither have police or the government. We will fight. It was the church that forced us on to the streets.”

Outrage at the case grew on Sunday when a state politician, PC George, asked a press conference why the nun had taken more than two years to raise the complaint. “No one has a doubt that the nun is a prostitute,” said George, an independent MP with a history of controversial remarks about sexual assault. “Why didn’t she complain the first time?”

The National Commission for Women, a statutory body that promotes women’s rights, called his remarks shameful and demanded a police investigation.

George Joseph, the president of the Joint Christian Council, one of the groups organising the protests, accused senior politicians and church leaders of interfering in the case. “It is the 76th day since the petition was filed and still police have not taken a major step in the investigation,” he said. “Police are interrogating the petitioner, not the accused, and we believe they are under pressure from political parties and the church.”