Hundreds of protesters are expected to gather at Oxford University after students voted to allow BNP leader Nick Griffin to speak at their union.
Controversial historian David Irving, who was jailed for Holocaust denial, has also been invited to the free speech event.
Their presence on the list of speakers had already prompted a series of high profile withdrawals from the platform, including Defence Secretary Des Browne.
Despite opposition, the Oxford Union Debating Society members voted by a margin of two-to-one to extend an invite to Mr Griffin.
Martin McCluskey, president of the Oxford Student Union, said it was "disgraceful" the pair were being given the same platform as past speakers who include Mother Theresa and the Dalai Lama.
Sabby Dhalu, secretary of campaign group Unite Against Fascism, said: "If the event goes ahead as it stands, it does not even have the appearance of a 'debate'. Oxford Union will have to hold itself responsible for any subsequent repercussions on the threats to the safety of students if it proceeds with this decision."
Lee Jasper, secretary of the National Assembly Against Racism, added: "Oxford Union is jeopardising the safety of the students by continuing with this event. It is not too late to rescind these invites - Oxford Union gathers growing condemnation with every moment it continues being complicit with facilitating a meeting promoting fascism and Holocaust denial."
Defending its decision, the Oxford Union Debating Society said it was important to give people of all views a platform. Luke Tryl, president of the society, said: "They will be speaking in the context of a forum in which there will be other speakers to challenge and attack their views in a head to head manner."
Mr Griffin, who was convicted in 1998 for incitement to racial hatred for material denying the Holocaust, has repeatedly insisted the BNP is not a racist group.
Mr Irving has insisted he was not a Holocaust denier - despite spending three years in prison for the crime.
