Eleven transgender prisoners were sexually assaulted in jails in England and Wales last year, it has emerged.
The figures, from the Ministry of Justice, cover inmates who were born and remained legally male but self-identified as female.
The total number of transgender victims far exceeds the number who were suspected of carrying out sex attacks, with only one such case in 2019.
The campaign group Stonewall called the figures "upsetting".
In a separate incident, it was unclear if the transgender individual involved was the assailant or the victim.
All of the alleged attacks occurred in the male prison estate, the prisons and probation minister Lucy Frazer said.
Last week, ministers revealed that out of 124 sexual assaults in five women's jails over the previous nine years, from 2010 to 2018, seven had been carried out by trans prisoners.
Ms Frazer said the total included those who were born female but identified as men, non-binary or intersex, as well as people who were male by birth and now identified as female.
One of the cases was that of Karen White, who sexually assaulted two women while on remand at New Hall prison in Wakefield in 2017.
White, who was born male and now identifies as a woman, was described by a judge as a "predator" who was a danger to women and children.
The case prompted an overhaul of guidelines for transgender prisoners and led to the establishment of a new transgender unit at HMP Downview, in south London.
Last year, there were 163 transgender prisoners in jails in England and Wales, 129 of them in men's prisons and 34 in women's prisons, an increase of 30 on 2018.
Most self-identified as female.
Self-identified is the term given to someone's personal sense of their own gender, the gender they live in and present as.
The figures, which were collected during April and May 2019, did not include prisoners who had transitioned from their birth gender and who have a full Gender Recognition Certificate.
In a statement, Stonewall, which campaigns for the rights of lesbian, gay, bi and trans people said the figures showed transgender prisoners faced a "high risk of assault, harassment and violence".
"We also know that they often face barriers to accessing healthcare, as well as being at risk of serious mental health problems and suicide," it said.
"It's essential that all prison staff are provided with high-quality training, so that they can ensure the safety and dignity of trans prisoners."
Prisons minister Lucy Frazer said: "All sexual assaults in prison are referred to the police and HMPPS (Prison and Probation Service) have strong safeguards in place to manage risks to all those in custody, regardless of their gender.
"HMPPS has robust processes in place to care for and manage transgender individuals in custody.
"The safety of all those in our care is of paramount importance.
"All known risks, both towards or presented by a transgender person in prison, will always be taken into account in their care and management.
"Individuals will be cared for and managed in the gender with which they identify, regardless of their location in a male or female prison."