The Hong Kong Journalists' Association (HKJA) says self-censorship is enormously difficult to detect. Indeed, the true circumstances surrounding Ms Mo's removal are shrouded in claims and denials. Nevertheless, it has raised the concerns of some legislators, who say they have received complaints from listeners about the presenter's removal and suspect self-censorship.

RTHK denies it axed Ms Mo from the radio show she co-hosted once a week for the past six years because she was too outspoken. 'Not true,' says acting assistant director of broadcasting Ava Wong Fat-chi. 'A change of presenters is normal in the course of programme reshuffles.' Ms Wong insists the talkback show will continue to be impartial. 'The presentation of the programme remains as tough and critical as ever.'

But her version of the decision process that removed Ms Mo from her Thursday-night slot - replacing her with regular anchor Cheung Siu-ying, who already presented the Monday-to-Friday show on other nights - does bear some resemblance to the presenter's reported explanation.

Ms Wong says Ms Mo needs to work on her on-air style. 'She has to improve her tone; it's a matter of politeness,' she says, adding Ms Mo was too abrupt with callers or guests. She also complains that Ms Mo had discussed on air the circumstances of her departure and read out messages from listeners.

A broadcasting-industry source close to government circles says Ms Mo was removed from the show because she was unpopular with senior officials. 'Some of the government people don't really like her. They don't like the way she criticises people.'

Ms Mo, an RTHK veteran, declined to comment to the South China Morning Post on the reasons for her being dropped. She remains a presenter of the English- and Cantonese-language editions of Media Watch, which is produced by RTHK and shown on TVB every week.

Sources close to Ms Mo say RTHK seemed to be willing to allow her to continue appearing on Media Watch because it is scripted. 'The radio show she was sacked from is spontaneous, live and uncontrollable,' says one colleague.

The allegations about Ms Mo's dismissal come as the electronic media is under increasing scrutiny over self-censorship allegations following recent press headlines about ATV and TVB's policy of referring to Chen Shui-bian as 'Taiwan leader' rather than 'Taiwan president'. The pro-Taiwan Hong Kong and Kowloon Trades Union Council highlighted the policy and urged them to refer to Mr Chen as 'president'.

The electronic media faced particularly strong charges of self-censorship during the transition to Chinese sovereignty, but the HKJA says it has come across few instances of programmes being axed in the past few years.

The incidents documented by the HKJA include the reluctance of the two television stations in 1996 to purchase a follow-up to the controversial British documentary The Dying Rooms, which portrayed mainland orphanages as places where babies were often left to die, and ATV abandoning in 1994 the popular current-affairs talk show, News Tease. In 1993, ATV decided not to air a Spanish documentary on the Tiananmen Square massacre, leading six journalists to resign. The same year, TVB purchased but failed to air BBC documentaries on late chairman Mao Zedong and mainland labour camps.

HKJA vice-chairman Gren Manuel says he fears staff at television stations are now so attuned to managements' reluctance to touch sensitive issues that they no longer purchase or seek to produce such programmes. He views the description of Mr Chen as Taiwan's 'leader' as symptomatic of the pressure to which the Hong Kong media has been subjected in recent years from mainland officials over the Taiwan issue. 'Last year, it was very clear that Taiwan was a bit of a test case [for self-censorship],' he says.

At TVB, journalists say they have been instructed to avoid using certain language and images which might upset Beijing. A source says management has distributed a memo telling journalists not to use the word 'massacre' to describe the June 4, 1989, slaughter of dissidents in Tiananmen Square - since it is viewed as laden with value judgments - and to use more neutral terms.

Nor are Taiwanese flags used in logos to introduce stories, although those of other countries are portrayed, says the source.

TVB news controller Loh Chan says he is not aware of any memo about the use of the term 'massacre'. But Mr Loh says the station preferred neutral terms to describe the June 4 crackdown, such as 'incident'. He says use of the word 'massacre' depends on the scale of the killing. 'Until this moment, we don't know the truth, we know there were a lot of casualties, [but] the Chinese Government has not released statistics.'

He says the Taiwanese flag is not used in graphics displayed while newsreaders are introducing stories about the island because of the 'one-China policy'. However, footage showing Taiwanese flags during news reports is not edited.

The HKJA 2000 report on media freedom, entitled 'Patriot Games: Hong Kong's media face to face with the Taiwan factor', raises concerns that Taiwan-related developments threaten freedom of expression. 'Most worrying have been statements by Chinese officials on the question of Taiwan's sovereign status and whether the media should be able to report views which contradict the Beijing position that Taiwan is an inalienable part of China,' the report states.

The Claudia Mo incident is not the first involving allegations of self-censorship at RTHK since its former chief Cheung Man-yee was transferred to head the SAR's trade office in Tokyo in 1999. Ms Cheung was known as a vocal defendant of media freedom, and her move triggered accusations that the Government was bowing to pressure from pro-Beijing figures who wanted her out.

Manuel says the HKJA is concerned about the suspension of the satirical current-affairs programme Headliner last September and its replacement by a series profiling people such as Chief Executive Tung Chee-hwa, executive councillor Leung Chun-ying and prominent business figures.

The suspended programme came under fire as 'anti-government' from RTHK critic Xu Simin, a member of the Chinese People's Political Consultative Conference Standing Committee who earned the nickname 'Cannon' for his broadsides.

The HKJA is lobbying for the government-funded broadcaster to be corporatised, in the same way as the BBC in Britain and the Australian Broadcasting Corporation have been put at arms' length from officials. 'It remains in effect a department of the Government,' says Manuel.

Frontier legislator Emily Lau Wai-hing, a former HKJA chairman, says: 'I am watching RTHK very closely, and I have repeatedly told the director of broadcasting that I am watching. I am very concerned, and I think RTHK is something of a symbol of media freedom which is watched closely by the international community. We don't want RTHK to give the impression that it is buckling under.'

Director of broadcasting Chu Pui-hing, who replaced Ms Cheung, says in response to questions from the Post that he is confident the community continues to support RTHK operating in an 'editorially independent framework'.

'There are bound to be different views about the performance of a public broadcaster, as is the case everywhere else, but we will certainly continue to uphold our editorial independence vigorously.'

However, senior RTHK staff are known to be concerned about the station's future editorial independence following the departure of former chief secretary for administration Anson Chan Fang On-sang, who was viewed as a staunch defender of media freedom. Even though her successor, Donald Tsang Yam-kuen, has spoken out strongly in defence of free speech, he is said to be particularly sensitive to media criticism of himself and the Tung administration.

Ms Mo's departure from the talk show appears to be a sensitive issue within RTHK. It was raised at an internal management meeting on Thursday, when a senior staff member reported that he had been contacted by a Post journalist preparing an article on the issue.

Ms Wong says: 'Since Open Line, Open View was first broadcast in 1994, more than 20 presenters have hosted the programme. A change of presenters is normal in the course of programme reshuffles.'

Democratic legislator Andrew Cheng Kar-foo says he raised the axing of Ms Mo from the radio programme with senior RTHK officials. After receiving what he describes as the 'official answer', Mr Cheng says he was surprised when an official told him Ms Mo 'spoke beyond a bit what she was supposed to say'.

'I certainly believe the replacement of Ms Mo on this programme is part of the self-censorship of RTHK,' he says.

Ms Lau says she received 'a lot of complaints' from listeners about the dropping of Ms Mo. 'They said she was good, and they do not understand why she was removed . . . This is a very bad signal.'

On the issue of labelling Mr Chen, RTHK says it is a matter of 'editorial judgment'. In Chinese-language news broadcasts, he is referred to as 'President Chen Shui-bian of Taiwan', says RTHK. In English-language news, he is called 'Taiwan president' or variations on that.

TVB's Mr Chan says Mr Chen is referred to as 'Taiwan leader, President Chen Shui-bian' on the Jade Cantonese-language channel. He says there has been no change in that practice since 1997 and insists the station has to be consistent with the 'one-China principle'. Mr Chan rejects allegations of self-censorship. Management is not involved in editorial decisions, he says.

ATV refused to comment and pointed to comments earlier this month from its deputy head of news, Tong Tak-chuen, who said ATV also advocates 'one China'. 'If we were practising self-censorship, we would not report any news about Taiwan. It is a fact that Mr Chen is a leader of Taiwan.'