According to the Telegraph, speaking at the Hay Festival, Professor Timothy Garton Ash called for a rethink on new counter-terrorism legislation.
He said: "Some of you may know that in the new counter-terrorism legislation, the securocrats in the Home Office are trying to impose on universities a so-called prevent duty, which would call on us to prevent event non-violent extremists speaking on campus.
"Now non-violent extremists? That's Karl Marx, Rousseau, Charles Darwin, Hegel, and most clearly Jesus Christ, who was definitely a non-violent extremists. The Home Office wouldn't want him preaching on campus.
"This is a real threat I think to free speech and one we have to fight back against."
Introducing his new book Free Speech: Ten Principles for a Connected World, he said it was not just the state that was endangering free speech. He said individuals are too quick to say they're offended.
He's calling on universities to "hold the line" in order for free speech to survive.