Free speech at UK universities is being put at risk, MPs and peers have warned.
A new report argues that free speech on campus is being hampered by factors such as intolerant attitudes and unacceptable behaviour, red tape and a lack of clear guidance.
It warns that whole universities cannot be "safe spaces" and they must be places where unpopular and controversial ideas can be heard and debated.
The findings, published by the Joint Committee on Human Rights, come amid continuing debate about free speech at universities.
There have been reports of speakers, debates, literature and organisations being opposed or criticised, often by student unions, societies or specific groups of students.
In its report, the committee concludes that, in general, there is support for the idea of free speech among students, and a survey of student union officers found that most said restriction of free speech was not a problem at their institution.
But it goes on to warn that, even though many concerns about free speech have come from a small number of incidents which have been widely publicised, "any interference with free speech rights in universities is unacceptable".
"We are concerned that such interference as has been reported could be having a 'chilling effect' on the exercise of freedom of speech more widely," the committee says.
The report notes that former universities minister Jo Johnson previously raised concerns about "no-platforming" and "safe space" policies being used to stifle discussion and cited student protests against events featuring speakers such as campaigners Peter Tatchell and Julie Bindel as examples of groups seeking to shut down debate rather than confront ideas.
The report says there is evidence that "safe space" policies - which aim to create an environment in which students can express themselves and are protected from harassment and discrimination - may restrict the expression of groups with unpopular, but legal views, such as pro-life organisations.
"Universities must be places where open and uncensored debate (within the law) can take place so students can think for themselves and develop their own opinions on ideas which may be unpopular, controversial or provocative," the report says.
"However, the concept of safe spaces is either too broad or very vague and therefore we do not find it helpful. University is an environment where a range of opinions should be heard and explored. Minority views should not be barred from student union premises."
The report also concludes: "Student societies should not stop other student societies from holding their meetings. The right to protest does not extend to stopping events entirely. Intimidating people exercising their free speech rights is particularly deplorable when meetings are invaded by masked protesters seeking to intimidate.
"Masked protest, intimidatory filming or physical disruption is unacceptable and must be stopped. Law enforcement agencies should take action when appropriate.
"Where student groups or bodies are inhibiting free speech rights in this way, universities should take disciplinary action to protect the right to free speech, in line with their statutory duty."
The report also calls for the Charity Commission, which regulates student unions as registered charities, to review its guidance, and that university codes of practice on freedom of speech should be clear, and help to enable debate, not restrict it.
Committee chairwoman Harriet Harman said: "Freedom of speech within the law should mean just that - and it is vital in universities. Evidence to the Joint Committee on Human Rights showed that there is a problem of inhibition of free speech in universities.
"While media reporting has focused on students inhibiting free speech - and in our report we urge universities to take action to prevent that - free speech is also inhibited by university bureaucracy and restrictive guidance from the Charity Commission."
Chris Hale, director of policy at Universities UK, said: "Universities are absolutely committed to promoting and securing free speech and will not allow legitimate speech to be stifled. There is already a legal duty on the higher education sector to secure free speech within the law and universities have developed policies in this area.
"As the report states, there is little hard evidence of a systematic problem of free speech in universities. But, despite the thousands of events that go ahead across the sector without incident, a small number of flashpoints and challenges do arise from time to time.
"It is important that universities are well equipped to secure free speech within the law, while balancing this with other responsibilities such as the safety of students and staff.
"We will look at the advice of the committee in this area and how it can complement the already extensive experience of managing such events and policies universities have in place.
"Universities must continue to be places where difficult topics are discussed and where people, however controversial their views, should be allowed to speak within the law, and their views challenged openly."
A spokesman for the Charity Commission said: "We recognise the important role that students' unions play in promoting or engaging in analysis, debates or discussions on controversial or sensitive issues.
"Our existing guidance is clear that charities can legitimately challenge traditional boundaries, encourage the free exchange of views and host speakers with a range of views.
"What we expect of student unions' trustees - as is expected of all charity trustees in accordance with charity law - is that when carrying out activities, they consider and take reasonable steps to assess and manage any associated undue risks to their charity and people who come into contact with it. "