Attempts to clamp down on extremism could give rise to a "police state", a chief constable has warned.
Sir Peter Fahy of Greater Manchester Police said it was for wider society to define the boundaries of extremism and not front-line police officers when faced with free speech issues such as radical Islamic preaching and anti-gay or anti-women's rights sentiment.
His comments come amid an attempt by the Government and security forces to combat radicalisation, as more than 500 people are thought to have travelled to Syria to fight with the extremist Islamic State (IS) group.
Referencing George Orwell's dystopian novel 1984, the vice president of the Association of Chief Police Officers (Acpo) told the Guardian: "If these issues (defining extremism) are left to securocrats the there is a danger to drift to a police state.
"I am a securocrat, it's people like me, in the security services, people with a narrow responsibility for counter-terrorism. It is better for that to be defined by wider society and not securocrats.
"There is a danger of us being turned into a thought police. This securocrat says we do not want to be in the space of policing thought or police defining what is extremism."
He said schools and universities needed to improve their policy on radical views and identify those considered vulnerable in order to "keep police out of schools and education".
"The police service does not want to be in school or on university campuses controlling thought but the best way to avoid this is for such institutions to have procedures to know the messages which are being promoted and for student bodies to have policies on whether preaching hatred towards homosexuality, allowing segregated meetings or advocating violent action overseas is acceptable or not," Sir Peter said.
In the Commons this week Home Secretary Theresa May fleshed out details of the Counter-Terrorism and Security Bill, which will include temporary exclusion powers, a ban on insurance companies footing the bill for terrorist ransoms and the reintroduction of powers to relocate terror suspects across the country.
A statutory duty will also be placed on named organisations such as colleges, universities, the police and probation providers to help deter radicalisation and, where organisations fail, ministers will be able to issue court-enforced directions.
The proposals have been met with opposition from human rights groups.