Hundreds of demonstrators are expected tonight outside the Oxford Union where two leading figures from the British far right are due to appear as speakers.
The historical writer David Irving and the British National Party (BNP) leader, Nick Griffin, have been invited to address the student forum – which styles itself as "the world's most famous debating society" – at 8.30pm.
They will talk on the subject of free speech, but the invitations have been widely condemned.
Trevor Phillips, chairman of the Equality and Human Rights Commission, accused the event's organisers of staging a "juvenile provocation" and reducing freedom of speech to "a silly parlour game".
He told the BBC's Andrew Marr Show yesterday: "As a former president of the National Union of Students, I'm ashamed that this has happened."
Some critics have appealed for the forum to be cancelled amid warnings that people may get hurt as tempers rise.
Julian Lewis, a shadow defence minister, who addressed the Union last week in a debate about the "war on terror", said the students should be "ashamed" of themselves. In a letter to the Union's officers and standing committee, Mr Lewis, the Tory MP for New Forest East, said he was resigning his life membership "with great sadness". Mr Lewis, who studied at Balliol and St Antony's colleges, said the right to free speech should not guarantee access to privileged platforms.
The invitation was also opposed by the university's Muslim and Jewish societies, but Oxford Union members voted by almost two to one in a secret ballot on Friday to go ahead with the invitation to both speakers despite signs of growing opposition.
Several senior politicians, including the Defence Secretary, Des Browne, have withdrawn from the event which was organised by the Union's president, Luke Tryl, a member of the Tory youth organisation, Conservative Forward.
Mr Tryl said: "[Mr Griffin and Mr Irving] 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."
Simon Darby, a BNP spokesman, described the event as an "important breakthrough" for the party. "It is ironic you have got people shouting 'fascism' while campaigning in the face of the process of democracy," he said. "Nick is looking forward to the event. It is easy to ignore the protests."
Mr Griffin heads a party that believes in banning almost all immigration to the UK, and whose manifesto calls for "two million plus" of those already here to be deported.
Mr Irving, 69, was once considered to be a promising historian, but became notorious after claiming that Hitler did not ordered the massacre of Jews, and denying that the gas chambers existed. Holocaust denial is a criminal offence in several countries, and in 2006 Mr Irving served a jail term after being convicted in Austria.
Sabby Dhalu, secretary of the campaign group Unite Against Fascism, said: "If the event goes ahead as it stands, it does not even have the appearance of a 'debate'.
"The 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, warned: "The 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 a meeting promoting fascism and Holocaust denial."
Martin McCluskey, president of the Oxford Student Union, the university's official student body, said it was "disgraceful" that the pair were being given the same platform as past speakers including Mother Teresa and the Dalai Lama.