A university free speech society has been told by the students' union that its inaugural speaker must submit his speech in advance for vetting.
UKIP MEP Bill Etheridge was invited to give a talk by the Liberate the Debate society at the University of Sussex.
Vice-president Edward Seccombe said the event in Brighton had "met significant resistance" from the University of Sussex Students' Union (USSU).
The USSU said it had been "working hard" to help ensure it could go ahead.
Frida Gustafsson, union president, said: "We want to unequivocally state that Bill Etheridge is, and always has been, welcome to address our members."
Mr Etheridge, the MEP for the West Midlands, said his talk would still go ahead "even if I have to stand outside those university gates".
He said: "I find it so ironic because all I want to do is discuss free speech.
"I have spoken at other universities across the country and had a rough ride from the students, which is what I expect.
"But I've never before had a university make it impossible for me to attend."
The union rated Mr Etheridge's planned talk on Friday about libertarianism and free speech as "medium to high risk".
"But they haven't said of what, and what the danger is supposed to be," the MEP said.
Mr Seccombe said he thought the union was probably worried that the MEP's presence on the campus would cause offence.
"It's a blatant attack on free speech," he said.
"The reason our society exists is because of this growing trend that student unions are restricting speech."