The head of Australia's Department of Foreign Affairs and Trade Frances Adamson has called on students from China and elsewhere to respect free speech on campus, saying efforts to interfere in university activities were an "affront to our values".

In remarks that appeared to be aimed at China, Ms Adamson, Australia's top diplomat and former envoy to Beijing, used a lecture at the University of Adelaide to urge the nation's universities to ensure they were not vulnerable to foreign influence. She said students and lecturers should be able to speak freely and called on all international students to "respectfully engage" with ideas that they may find unusual or contentious.

Addressing international students at the university's Confucius Institute, which receives funding from the Chinese government, Ms Adamson, who holds a position equivalent to a Singapore permanent secretary, said students should ensure that discussion and debate remained "respectful and patient".

In a speech last Saturday, she said: "No doubt, there will be times when you encounter things which to you are unusual, unsettling, or perhaps, seem plain wrong.

"When you do, let me encourage you not to silently withdraw or blindly condemn, but to respectfully engage. The silencing of anyone in our society - from students to lecturers to politicians - is an affront to our values."

Ms Adamson's comments made national headlines and come amid a growing debate about the conduct of some Chinese students at Australian universities.

There have been concerns that China has attempted to interfere with activities on university campuses, including using student organisations to monitor Chinese international students and local teaching staff.

On at least four occasions this year, Chinese social media campaigns and Chinese diplomats in Australia have targeted academic staff in Australian universities over teaching materials deemed "offensive". The furores have resulted in apologies from academics but also prompted concerns about Chinese interference in academia. In June, an academic at the University of Sydney said Chinese consulate officials asked the university to reconsider holding a forum on the Tiananmen Square protests, which took place in Beijing in 1989.

According to a report in The Australian newspaper, the academic, Professor John Keane, said "these things are not unusual" and the university refused to cancel the forum.

Australian Education Minister Simon Birmingham yesterday endorsed Ms Adamson's remarks.

Speaking to ABC News, he said: "Universities need to be as ever vigilant today as they have been through their history in terms of ensuring their integrity, their high standing.

"Every student should be challenged when they are at university. They should have their thinking challenged, and they should find it a challenging experience." Australia has a booming international education sector. As of July, there were about 565,000 foreign students enrolled in schools, universities and other education facilities in Australia.

The largest source was China, which provided about 29 per cent of foreign students, followed by India with 11 per cent, and Nepal, Malaysia and Vietnam, each with about 4 per cent. Almost 350,000 students - including about 7,000 Singaporeans - were enrolled in universities, up 17 per cent from last year.

But the growth of the sector has raised concerns that the reliance of universities on fees from Chinese students may affect the institutions' willingness to combat any attempt to unduly interfere in campus activities.