CANBERRA, Australia — A survey of more than 30,000 Australian university students released on Tuesday found that half the respondents had been sexually harassed and almost one in 50 had been sexually assaulted on campuses, but few made formal complaints.

The Australian Human Rights Commission, which surveyed students across all 39 universities in 2015-16, concluded that sexual assault and sexual harassment occurred at unacceptable rates at Australian universities.

The survey found 51 percent of respondents were sexually harassed at least once in 2016.

It also found 6.9 percent of respondents reported being sexually assaulted in 2015 or 2016, with 1.6 percent saying the assaults occurred in a university setting.

But only 9 percent of those sexually assaulted and 2 percent of the sexually harassed in the past two years had made formal complaints.

The commission recommended that universities ensure that staff and students representatives likely to hear such disclosures receive training to respond. It also urged universities to pay for surveys every three years to track progress in reducing such harassment and assaults.

The commission also recommended that university residences and residential colleges fund a review of factors that contribute to sexual misbehavior in their settings.

Universities Australia said the 39 universities that the advocacy organization represents shared a commitment to do more to ensure every student was safe and could study in an environment where respect was paramount.

“We send a strong and clear message today that these behaviors are not acceptable. Not on our campuses and not in Australian society,” chair Margaret Gardner said.

The National Union of Students accused universities of allowing rape cultures to develop on campuses around the country.

“Universities can no longer bury their heads in the sand and ignore sexual assault and harassment,” the union women’s officer Abby Stapleton said.

The union wants universities to establish a national complaints and compliance mechanism and maintain comprehensive records of assault and harassment reports.