The reports, obtained by The Sun Herald and The Sunday Age under freedom of information laws, reveal almost all Australian National University undergraduate colleges were given the bottom ranking for both their sexual assault policies and how often they were applied.

All undergraduate colleges but one were given the lowest rating for the confidence residents had in the university's response systems and reporting procedures for sexual assaults.

The colleges performed better in other areas explored by the reports, including hazing, substance abuse and security.

Colleges were marked on each measure with either "good progress", "making progress" or "needs development", based on survey responses, one-on-one interviews and focus groups with students, staff and alumni.

The reports by consultancy Nous were handed to the ANU in December as part of an internal review. The review was sparked by a landmark Australian Human Rights Commission survey that found one in 15 Australian university students reported having been sexually assaulted at least once in 2015 and 2016.

The ANU released a university-wide report at the end of 2018 that flagged a "significant level of dissatisfaction among residents" over college responses to sexual assault and harassment. But it chose to keep the more detailed, college-specific reports secret, citing privacy concerns.

"ANU decided not to release individual reports for student residences out of respect for the privacy of survivors who provided meaningful accounts of their experiences in their places of living," a university spokesman said. "Our concern was that these individuals would be readily identifiable among their peers and fellow residents from the accounts they provided."

The college-specific reviews called for the university to immediately update its sexual violence reporting procedures to ensure students arriving at residential halls at the beginning of 2019 had greater guidance - a timeline not revealed in the university-wide report published last year.

The university has not updated the sexual violence reporting procedures that govern the bulk of its residences and instead will announce a new sexual violence prevention strategy and sexual misconduct policy next month.

"ANU is working closely with all student residences to develop cultural action plans to make change in individual residences," the spokesman said. "These plans will be ready to roll out by mid-October."

Burgmann College and Johns XXIII College, which house ANU students but were set up by the Anglican and Catholic churches respectively, updated their sexual violence reporting procedures by the beginning of 2019.

ANU student leaders last month went on strike during the university's open day due to a clash with management over price hikes, pastoral care and sexual misconduct. At the time, the leaders said a reduction in the number of college staff meant more sexual assaults and mental health incidents were being disclosed to senior student residents.

More than 5000 of ANU's 25,000 students live at one of the dozen residences, including two postgraduate colleges, covered by the reports. Two new colleges opened this year.

A second national survey on sexual assault and harassment at Australian universities will be conducted in 2020 by the Australian National University's Social Research Centre.