The concept of academic freedom is "impoverished" and under threat at a time when the vogue is for arguing that freedom of speech must be limited to protect certain groups.
The warning has been issued in advance of an International Academic Freedom Day organised by the campaign group Academics for Academic Freedom (AFAF).
The group's founder, Dennis Hayes, argues that "there are no high-profile defenders of 'absolute' free speech and academic freedom".
He points out that Shami Chakrabarti, the director of Liberty, is "fond of noting that there are limits to free speech" and that the British Library's Taking Liberties exhibition included a section on "Free speech and its limits".
"No defence of unqualified free speech comes from where you might, however naively, expect it," he says.
He also suggests that the argument that limits are needed to protect groups from threats by racists, fascists and extremists implies that these groups are vulnerable, a view that amounts to contempt, he says.
Dr Hayes concludes: "Academics have a choice. To become another profession with no 'noble' goals or to accept responsibility to defend free speech and academic freedom and hope to make the ivory tower a beacon for the defence of freedom in wider society."
Dr Hayes made the argument in a special edition of the British Journal of Educational Studies, which will be launched on 20 May at an AFAF seminar chaired by Ann Mroz, editor of Times Higher Education.
The AFAF has declared this date (the birthday of the political philosopher John Stuart Mill) International Academic Freedom Day.
It is asking academics and students to hold seminars, discussions and protests on the topic.