Students who have been raped are having to wait up to four weeks for counselling services at some universities.
Advocates also claim those who have dropped out of their degrees after suffering a sexual assault have been refused counselling because they are no longer enrolled.
The revelations come in the lead-up to the release of a landmark survey of 39,000 students on sexual assaults at campuses.
The strain on counsellors has pushed caseworkers at universities - including University of Sydney, UNSW, Monash University, UTS, and Deakin University - to join with End Rape on Campus, advocate against sexual assault Nina Funnell and NSW politicians to call for the establishment of a national 1800 hotline for distressed students.
Notices posted online in May from Curtin, Bond and the University of Adelaide show high demand for counselling services, with wait times of up to four weeks.
One rape victim, who cannot be identified for legal reasons, said she had sought counselling at her university following an alleged assault, and was cut-off from the service after she dropped out of her degree.
"It's just beyond belief," she said. "It's so despicable to say I could access counselling and then block me off."
In February, universities were accused of "actively covering up sexual assaults" after a submission to the Human Rights Commission alleged there had been just six expulsions in the past five years, despite more than 500 official complaints.
Following community pressure, all of Australia's universities are now set to simultaneously release data on sexual assaults on their campuses when the final report is released in August.
End Rape on Campus Australia director Sharna Bremner said that in several cases the group had been unable to refer assaults to their own university counselling facilities "because those facilities are already stretched beyond capacity".
Ms Funnell, a sexual assault survivor, has led the push for a national hotline. She said the survey results would stir up dormant trauma in the community, including for those aged in their 30s, 40s, 50s and 60s who had been assaulted during their university years.
"These people can't access university services," she said. "No one has done any impact planning. No one has provided any additional resourcing to the frontline sexual assault services who are currently expected to deal with the fallout caused by this inquiry."
Sex Discrimination Commissioner Kate Jenkins has urged universities to ensure that they have adequate support services in place in the lead-up to the release of the report.
Sexual assault survivor and NSW Labor MP Jenny Aitchison said: "The release of the report in August means an investment in expert services with capacity to cope with the expected increased demand for counselling services is urgent.
"For too long universities have done the bare minimum in terms of prevention, reporting and responding to sexual assault and violence on campus."
Ms Aitchison urged peak body Universities Australia to commit to funding the hotline, which has been costed at $1.3 million. The body's current hotline, 1800 RESPECT, operates on a triage model in which not all calls are answered by trauma counsellors.
Universities Australia chief executive Belinda Robinson said the body was investigating "global best practice as the sector gives careful consideration to a range of options to support students".
"We recognise that the release of the national report in August is likely to see a rise in the number of students seeking support," she said.
"We are working closely with our member universities to ensure resources are in place to provide students with support at that time."
