'There is a benchmark for English ability in terms of teaching,' Professor Tsui said. 'There should be a policy in place to say that teachers at this university should have a certain level of English.'

Professor Tsui, who was appointed to the newly created post last week, was speaking at a forum on the role of English as the medium of instruction and lingua franca at the university.

She said the HKU community needed to have a dialogue on which language students and academics should use on campus - whether communicating in class or informally, and possibly even in activities run by student societies.

On paper, HKU is an English-language institution, with the exception of classes such as foreign languages and Chinese literature. In practice, however, many lectures and tutorials run by local academics are conducted in Cantonese if no international or mainland students are present.

Professor Tsui said an official survey had found the English usage was lowest in group discussion work, where less than 20 per cent was conducted in the language. But staff were divided over whether students should be forced to use English.

'Those who are in support of this policy say it is essential to give students opportunities to express themselves in the language,' she said. 'Those against say it is important for students to be able to use their strongest language.'

However, English was the language of international discourse.

'There is nothing sacrosanct about English, except that it is the language that everybody understands,' Professor Tsui said.

'In 50 years, the lingua franca might not be English, it could be Putonghua. At that time we might be having the same discussion about how to promote the use of Putonghua.'

Her views were reflected by some other academics at the forum.

'If Hong Kong wants to be a world-class city, more than just having that slogan, I think we have no choice that all academic activities should be conducted in English,' said Paul Cheung Ying-seung, professor of electrical engineering.

He conceded that working entirely in their second language would create 'frustrations' for Cantonese-speaking students, but not forcing them to use English would hamper their development of language skills in the long term.

'If you don't go through that painful process, the turning point never comes, you get stuck,' Professor Cheung said.

However, some speakers also warned about the possible negative effects of imposing English use through enforcement.

Postgraduate student Howard Tam said he was concerned it could produce similar backlash as caused by the rules about the use of French in his native Canada to appease the Quebec lobby.

'People resent it. They say, why do I have to learn this language?' he said. 'I don't think HKU should think about introducing language police.'

Student union president Wan Hon-san said the union had been pushing student societies to use more English in e-mails and to hold events in English to promote inclusion of non-local students. However, the results had been mixed.

'When activities are held in English, most of the participants are international students,' he said. 'Local students will not be interested.'

Brian Darvell, professor of dentistry, said the talk of promoting the use of English through obligation had placed the discussion 'on the wrong foot'.

'It should be an expectation and you need to instil that expectation into students,' he said. 'If we are to be an international institution, we need to teach people to go outside of Hong Kong. You won't go very far if you only speak Cantonese.'