The University of Sydney has rejected calls from its staff to make a public statement in support of marriage equality.
Vice-chancellor Michael Spence reiterated his belief that advocating a "yes" vote would compromise the institution and have "a potentially chilling effect on debate".
But staff claim the university's neutral stance is out of step with other Australian universities.
A delegation of staff rallied outside the office of the vice-chancellor on Thursday to deliver an open letter that also called on the university to encourage its students, staff and alumni to vote "yes" in the same-sex marriage survey, which closes on November 7.
The letter addressed to Mr Spence and the university's chancellor Belinda Hutchinson criticised the failure of the university to adopt a stance in favour of same-sex marriage.
"We are troubled by your suggestion that, if the University of Sydney adopts a substantive position on a non-binding postal survey, our position would have 'a potentially chilling effect on debate'," the letter said.
"We can see that open and respectful debate is, on face value, worth striving for. However, the very question of marriage equality appears predicated on an over-arching lack of respect for people in the LGBTQI+ community."
Mr Spence responded to questions from Fairfax Media with a statement originally made to staff at the beginning of the marriage equality postal survey.
"I do not believe it appropriate for us to adopt an institutional position," he said.
"In saying so I want to stress that I do not mean to sound insensitive to the very real pain experienced by those currently unable to marry under Australian law. But I think the issue goes to (the) heart of the function of the university as an institution."
"Universities in the secular liberal tradition are essentially for a debate in which ideas can be freely expressed and discussed."
Mr Spence said this role would be compromised if a university as an institution adopts a substantive position on any given issue and begins to advocate it.
However, he acknowledged the university had adopted substantive positions in conducting its own business: "That is why, for example, we are committed to managing our endowment in a way that reduces its carbon footprint."
National Tertiary Education Union branch president Kurt Iveson said the union rejected Mr Spence's argument that the university should maintain a neutral position.
But he said: "The church that he's a reverend in has donated money to the 'no' cause so I imagine that has put him in a difficult position."???
An Anglican priest, Mr Spence did not answer a question about whether his religious beliefs had influenced his views on same-sex marriage.
NTEU spokesman Martin Rorke said the failure of the vice-chancellor to publicly support same-sex marriage was a dereliction of his pastoral duties: "Personally, I'm ashamed and appalled by this refusal to support LGBT staff and students."
The letter, signed by about 400 people, states the university's claim to support equal opportunities in education and employment "rings hollow, knowing LGBTQI+ students and staff are discriminated against and the university is not willing to publicly defend their rights".
The letter also states the university is "sending mixed messages" to LGBTQI+ staff and students by not endorsing marriage equality, yet claiming to support diversity.
"If the provost is willing to march in Mardi Gras to support diversity, we urge you, as vice-chancellor and chancellor, to formalise the university's position on same-sex equality, by publicly supporting same-sex marriage."
The open letter was organised by the NTEU, which noted that 65 academic bodies have endorsed marriage equality, including universities such as Monash, UTS, La Trobe, RMIT, University of WA and Macquarie.
A number of staff at the University of Sydney have also expressed support for same-sex marriage on social media, including members of the School of Literature, Arts and Media and the University's research portfolio.
However, support for same-sex marriage among staff is not universal, with part-time law lecturer Sophie York a prominent supporter of the "no" campaign.
The university has also been the site of clashes between supporters and opponents of same-sex marriage, with police called after hundreds of protesters confronted a "vote no" rally in September.