David Cameron has attacked British universities for not doing enough to tackle extremism on campus and singled out the Islamic charity CAGE for criticism.
The prime minister blamed political and cultural sensitivity among university staff as the reason "Islamist extremist" speakers are invited to speak.
"When David Irving goes to a university to deny the Holocaust – university leaders rightly come out and condemn him," Cameron said. "But when an Islamist extremist goes there to promote their poisonous ideology ... too often university leaders look the other way through a mixture of misguided liberalism and cultural sensitivity."
Cameron also attacked the National Union of Students for its alleged support of the controversial Islamic advocacy organisation CAGE.
CAGE made international headlines after it was accused of supporting and condoning Mohammed Emwazi the British man identified earlier this year as the notorious ISIS fighter "Jihadi John".
The NUS was faced criticism earlier this year after it agreed to work with the group to oppose the upcoming counter-terrorism bill.
"When you align yourself with CAGE, which called Jihadi John a 'beautiful young man' ... it shames your organisation," Cameron said.
It is the first time the prime minister has singled out the organisation for criticism in a public speech.
Cameron also announced plans to allow parents to cancel their children's passports if they fear they could join ISIS.
"I know how worried some people are that their children might turn to this ideology and even seek to travel to Syria or Iraq," he said.
"So I can announce today we are going to introduce a new scheme to enable parents to apply directly to get their child's passport cancelled to prevent travel."
The statement came in a speech about the government's counter-extremism strategy.
I'll be making a major speech on extremism today - how we can tackle the poisonous Islamist ideology that is so hostile to British values.
Monday's speech, which Downing Street aides dubbed one of the most "significant" since the general election, argued that more should be done to "take on nonviolent extremism" and "give incentives to communities to integrate more to reduce the risk of radicalisation".
Cameron also offered funding to organisation willing to work in anti-radicalisation movements: "What we are fighting, in Islamist extremism, is an ideology. It is an extreme doctrine. And like any extreme doctrine, it is subversive."
He also criticised other nonviolent groups deemed to be extremist by claiming they promote "ideas based on conspiracy" in order to deliberately [humiliate] Muslims" and "destroy Islam".
"You don't have to support violence to subscribe to certain intolerant ideas which create a climate in which extremists can flourish," he said.
The prime minister said more needed to be done to curb "nonviolent Islamism" that could lead people to join groups like ISIS.
"When you look in detail at the backgrounds of those convicted of terrorist offences," he said, "it is clear that many of them were first influenced by what some would call nonviolent extremists. It may begin with hearing about the so-called Jewish conspiracy and then develop into hostility to the West and fundamental liberal values, before finally becoming a cultish attachment to death.
"Put another way, the extremist worldview is the gateway, violence the ultimate destination. So people today don't just have a cause in Islamist extremism... In ISIL, they now have its living and breathing expression."