More than 350 people have signed a petition which accuses Prof John Finnis of "a long record of extremely discriminatory views against many groups of disadvantaged people".
The emeritus professor of law and legal philosophy told The Oxford Student newspaper: "The petition travesties my position, and my testimony in American constitutional litigation.
"Anyone who consults the Law Faculty website and follows the links in the petition can see the petition's many errors.
"I stand by all these writings. There is not a 'phobic' sentence in them."
The petition alleges that Finnis described homosexuality as "destructive".
It also alleges he compared homosexual acts to bestiality in a 1994 paper published by the Notre Dame Journal of Law, Ethics and Public Policy.
The article, called 'Law, Morality and Sexual Orientation', says "the deliberate genital coupling of persons of the same sex is repudiated...".
Signatories also urge the University of Oxford to "clarify its official position" on academics who hold discriminatory views.
A spokesperson for the institution said: "Oxford University and the Faculty of Law promote an inclusive culture which respects the rights and dignity of all staff and students.
"We are clear we do not tolerate any form of harassment of individuals on any grounds, including sexual orientation.
"Equally, the University's harassment policy also protects academic freedom of speech and is clear that vigorous academic debate does not amount to harassment when conducted respectfully and without violating the dignity of others.
"All of the University's teaching activity, including that in the Faculty of Law, is conducted according to these principles."
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