One of the more notable of these attacks was from Hao Tiechuan, director general of the department of publicity, culture and sports of the central government's liaison office in Hong Kong. Hao lambasted as 'illogical' a poll by Chung last December which found that the percentage of Hongkongers who identified themselves primarily as 'Chinese citizens' was at a 12-year low.

Other speakers at the Legco hearing shared Chung's worry that the core value enshrined in Article 137 of the Basic Law, which states that 'educational institutions of all kinds may retain their autonomy and enjoy academic freedom', was at risk following a spate of controversies.

Among the most prominent of these incidents was the row over University of Hong Kong's heavy-handed security arrangements for a visit by Vice-Premier Li Keqiang to mark HKU's centenary celebrations last August. Li was given the most prominent seat at the ceremony, triggering allegations from staff and students that the university was trying to ingratiate itself with the rich and the powerful.

Other incidents raising questions about institutions' commitment to academic freedom include the row that erupted in late January over the early release of a poll on the chief executive race by the former dean of Baptist University's School of Communications, Professor Zhao Xinshu.

An interim version of the poll, compiled before all responses had been received, showed a closer gap between the two leading candidates - Henry Tang Ying-yen and Leung Chun-ying - than in the final results. This led to charges of a bias in favour of Tang, and to Zhao's resignation the following month.

In another incident, Dr Dixon Sing Ming, a political scientist at the Hong Kong University of Science and Technology, was singled out for attack in 20 articles in pro-Beijing newspapers in recent months. They branded him and Chung - along with political commentator Ivan Choy Chi-keung - as subversive, anti-Beijing and anti-government sympathisers.

Sing was singled out for pointing to possible vote-rigging in last November's District Council elections, which saw a big defeat for pan-democrats, and supported the controversial de facto referendum on democracy triggered by the resignation of five legislators in early 2010.

'We do not serve any political party. We are just public intellectuals who speak the truth,' said Sing, who has been dubbed by the pro-Beijing press as the 'Long Hair' of the academic circle, in reference to radical legislator Leung Kwok-hung. 'Letters have been sent to the dean of my faculty trying putting pressure on the university to sack me.'

Undersecretary for Education Kenneth Chen Wei-on told legislators at the March 12 meeting that everyone is entitled to freedom of speech in a free and pluralistic society like Hong Kong. HKUST vice-president Dr Eden Woon pledged that Sing would continue to enjoy respect and freedom.

In support of Sing and in defence of academic freedom, 633 college and university teachers signed a petition and placed an advertisement listing their names in a Chinese-language newspaper.

But Sing told the same Legco meeting that the barrage of criticism struck him as Cultural Revolution-style tactic and expressed disappointment at the lack of response from senior university management.

'I have asked my colleagues whether they will exercise self-restraint in the future after seeing what happened to me, and they said 'yes',' Sing said.

Sing also questioned Chen's commitment to academic freedom, saying that Hao, as a mainland official, had interfered in Hong Kong affairs by criticising Chung's polls and that Hao's comments had amounted to a form of political pressure.

The vast pool of research funding and opportunities for key research collaborations on the mainland makes it less likely for university chiefs to risk upsetting ties with the mainland by protecting outspoken academics, he believes.

'I don't see how we can pin our hopes on university presidents or media bosses to safeguard academic freedom,' Sing said. 'We have to rely on the scholarly community and mass mobilisation.'

That is what Chung is championing with his 'civil referendum' campaign scheduled for tomorrow, when Hongkongers will be able to vote for their favourite chief executive candidate online, in a mock exercise two days before the 1,193-member Election Committee chooses Donald Tsang Yam-kuen's successor.

Chung, who has called on school teachers to set an example of civic participation by joining the mock election, shares Sing's concerns about a declining commitment to academic freedom in Hong Kong.

'I did not seek help from my own university because I have a stiff spine,' he said. 'But I am concerned that young scholars may be scared in the future by similar verbal attacks. There is a need to improve university culture, to hold more talks on the traditional role of intellectuals.'

Academic freedom is put at risk by more factors than just political pressure alone. One is the preoccupation with international rankings, such as those compiled by Times Higher Education, whose latest poll includes three Hong Kong institutions in the world's top 100 by reputation.

The poll canvassed the views of more than 17,000 academics on the academic prestige of 6,000 universities worldwide, and ranked HKU 39th, up from 42nd last year. HKUST rose from the 90-100 band to 61-70, while Chinese University made it to the top 100 for the first time.

Phil Baty, the editor of the rankings, warned that it was important for institutions to uphold academic freedom if they wanted to climb further up the list, now topped by American and British universities.

However, some academics see the pursuit of rankings as partly to blame for at least some of the threats to academic freedom in Hong Kong by increasing the workload of academics, who now more than ever have to go through the laborious process of applying for grants.

'Universities have put much resources on image building and give much publicity to students' results, teachers' backgrounds and research output,' Chung said. 'This is like pursuing the means to ends rather than the ends themselves. Universities have organised many activities to generate revenue, leaving little room for serious intellectual activities.'

There is also subtle pressure on research focus. Again, for the sake of getting a higher international ranking, universities give more funding to departments whose research output is published in top English-language journals, sidelining local research.

'It is much harder for research on say, Tai O, to get published in top academic journals than that on China studies,' said Dr Ma Shuyun, a government and public administration professor at Chinese University.

'Even French or Japanese research has a lesser chance of being cited in English journals that carry weight in international-ranking exercises. There is increased pressure on us to follow the rules of the ranking game, which has resulted in emphasis on certain kinds of research.'

Another push towards conformity comes from the outcome-based learning approach now widely practised across institutions. To enhance teacher effectiveness and accountability, administrators often require professors to produce documents identifying goals for courses and programmes and the methods to measure whether the outcomes have been achieved.

The need for approval for such documents requires numerous additional meetings to be held at faculty and departmental levels, eating into academics' time.

'It is reasonable to let students know what they can learn from a course in general but we are asked to comply with a certain format, use certain terms in the documents for bureaucracy's sake rather than education,' said Ma, comparing his workload to that of a school teacher. 'If university is a place for exploration of unknown knowledge, then how can we specify learning outcomes beforehand? Moreover, education is not just about learning in its narrow sense; it is also about impact on students' life, which we never know how and when it will take place.'

Ip Kin-yuen, a former academic and now chief executive for development at the Hong Kong Professional Teachers' Union, believes academic freedom is something that needs to be taught: 'Teachers can nurture a cherishing of the value of academic freedom in class, apart from only defending it.'