A new legal duty forcing universities to combat extremism on campus will "protect impressionable young minds", David Cameron has said.

The Government urged the National Union of Students (NUS) to drop its opposition to the anti-radicalisation strategy, which critics have claimed will create a culture of suspicion at academic institutions and could restrict freedom of speech.

Whitehall's Extremism Analysis Unit claimed at least 70 events featuring hate speakers were held on campuses last year and security officials also have concerns about the number of young people being radicalised and travelling to join Islamic State jihadists.

The Prime Minister, who will chair the first meeting of the extremism taskforce since the General Election, said: "All public institutions have a role to play in rooting out and challenging extremism.

"It is not about oppressing free speech or stifling academic freedom, it is about making sure that radical views and ideas are not given the oxygen they need to flourish.

"Schools, universities and colleges, more than anywhere else, have a duty to protect impressionable young minds and ensure that our young people are given every opportunity to reach their potential. That is what our one nation government is focused on delivering."

Nicola Dandridge, chief executive of Universities UK, said institutions already had procedures in place before external speakers are given the green light to address students.

"Universities must continue to be places where controversial subjects can be discussed openly, and flawed or dangerous ideas challenged. All universities have protocols and procedures that have to be satisfied before external speakers are given the green light to speak at a campus event."