The number of sex assaults in Islington’s two prisons have been revealed, prompting calls for an inquiry.

At Pentonville there were 14 sexual assaults on other prisoners or staff from 2006 to 2010.

At HMP Holloway, a women’s prison, there were five sex assaults during the same period.

The Ministry of Justice, who provided the figures as part of a Freedom of Information request, say they include both proven and unproven allegations and are subject to change because some alleged incidents are removed or reclassified following investigation.

Mary Mason, chief executive of Solace Women’s Aid who run Rape Crisis North London, said: “I find those figures quite shocking.

“That many rapes and sexual assaults in prison seems really high –- that is almost three a year in HMP Pentonville. It’s awful.

“If someone is in prison you would have thought it is possible to stop them getting raped. The right figure would be zero.

“We know rape is about power rather than sex, and to have that happening to vulnerable people in prison suggest there are serious control issues, as well as huge safety issues.”

She added: “I would want an investigation into why rape and sexual assault is so prevalent in Pentonville.”

A Ministry of Justice spokesperson said: “We take the responsibility of keeping staff, prisoners and visitors safe extremely seriously. That’s why we have a violence management system in place to deal with incidents quickly and robustly – any serious violence is immediately referred to the police.”

As of August 2010, the inmate population of HMP Pentonville was 1,233 and 459 at HMP Holloway. 459.