The news was delivered last month during a staff meeting at UC College but management have been monitoring a sharp fall in revenue for the past four years.

The college, which is now majority owned by private provider Navitas, offers pathway courses into tertiary study for domestic and international students.

Carol Drew has taught at the college for the past 20 years but said the first she'd heard of its financial woes was at the meeting in April.

"People are shell-shocked," she said. "We knew international student numbers were falling, just from seeing class sizes, but the whole thing has blown up very suddenly.

"If this was a problem for so long, why hasn't anything been done? It might have behind the scenes but we weren't told."

Management have called for voluntary redundancies, and enterprise bargaining with staff has been delayed as the college weighs its options.

Director and principal Jo Asquith said the college was reviewing "all aspects of its operating model in order to create and secure a successful long term future".

"We are committed to open and transparent communication with our employees and have commenced formal consultation with the [union] and staff."

She declined to comment further. It is understood the college has presented four strategies to escape insolvency to its board, having conducting two financial reviews since August.

A Navitas spokeswoman did not answer questions on the college's finances, staffing or enrolment numbers but said about half of current students were domestic.

Ms Drew said international student numbers had dropped off in the past few years.

"In one course, where you would have had 100, you've got about 20," she said.

At the same time, a Commonwealth cap on domestic student places in universities had filtered through to the college, she said.

But, at the National Tertiary Education Union, Rachel Bachl said there was more to the picture than declining student numbers.

"[This] is another example of the pitfalls of privatisation in higher education," she said.

"UC College has suffered years of mismanagement and neglect and it's now students and staff who are left to pay the price.

"When Navitas came in, it was all about growing international student numbers. What have they been doing?"

According to internal figures presented to staff, teaching costs currently absorb 48 per cent of college revenue, a figure management claimed was higher than a sample of other comparable providers.

But, the union says UC College had already been crippled by cost cutting, including some redundancies, since it was partially bought by Navitas in 2015.

Ms Drew said there were about 14 full-time teachers left, alongside part-time or casual staff. Many were older teachers, concerned about getting another job, most were women.

"There's been a push to casualise the work force across the whole sector," Ms Drew said.

"It's the young ones my heart really goes out to. They've got new mortgages and new babies."

The university still owns 49 per cent of the college and is understood to have equal weight on its board.

A spokeswoman do not answer specific questions about the university's plans for the college but said it valued alternative entry pathways for students into higher education and was "committed to creating those opportunities".

The union is now calling on Navitas as well as the university and the ACT government to act fast to guarantee the future of the college.

Higher Education Minister Meegan Fitzharris said the government had not been approached about the issue as yet. While it worked closely with the sector, she said financial decisions were up to individual institutions.