BNP leader Nick Griffin may be set to speak at an Oxford Union debate this week.
The far-right MEP has been invited to argue over the motion: "This House Would be Glad to Have Gay Parents".
Although it is unclear whether or not Mr Griffin has accepted the invitation, anti-fascist campaign group Hope Not Hate urged students to say no "to Griffin spreading his vile hatred.
"Despite their assumed privilege, will the Union never learn?" they said.
Judith Flacks, campaigns director for UJS, tweeted that the invitation was "unacceptable" and said it should be withdrawn. "Stop actively inviting BNP leaders to speak on campus," she wrote in a message directed at the Union. "Start realising your responsibility to student welfare."
In November 2007, the Union invited Holocaust denier David Irving and Mr Griffin to a debate on free speech, prompting a protest organised jointly by the Union of Jewish Students and Oxford University's Islamic Society. More than 2,000 people demonstrated against the event and proceedings were disturbed but it still went ahead.