Legal advice from the Equality and Human Rights Commission was welcomed by Labour, after stating that gender segregation, such as seating men and women separately at an event, is not permitted at events which are not acts of religious worship.
UUK, which represents 132 universities, faced a major political backlash in December after it published guidance on the voluntary segregation of men and women at campus events.
The controversy hinged on a case study, in which an external speaker was invited to talk about his orthodox religious faith and who subsequently requests segregated seating areas for men and women.
University officials should consider both freedom of speech obligations, as well as discrimination and equality laws when considering the request, UUK said.
Granting the request might be “appropriate” if neither men nor women were disadvantaged by the move, the UUK guidance said.
But the advice was roundly condemned by politicians, who accused UUK of pandering to religious extremism.
UUK eventually withdrew the case study after David Cameron joined the criticisms.
Chuka Umunna, the shadow business secretary, who said he was “horrified” at the original advice, welcomed the new guidance, saying it “makes it clear to universities and student unions that, outside of religious worship and practice, gender segregation is unlawful and should be prohibited at all times.
“Labour is clear that we would not tolerate segregation in our universities.”
The EHRC, which was asked to review the guidelines after the UUK controversy, says gender segregation outside religious worship is likely to be considered “unlawful” by the courts, and amounts to discrimination if it results in disadvantage to any participant because of their gender.
Genuinely voluntary gender segregation is permissible under the law, but it would be “impracticable for organisers to attain the necessary certainty that, at every stage, segregation was demonstrably voluntary” and there should be no explicit or implicit expectation that men and women should sit separately, it adds.
The safest approach is to ensure that there is no encouragement of segregated seating by gender, other than in acts of religious worship, it says.
A spokesman for Universities UK said it had updated its guidance to take account of the EHRC advice.
“Enforced gender segregation is never acceptable,” the spokesman said.