The physical challenges faced by Chee Soon Juan will be identical to those confronted by any athlete who has attempted a marathon, but the purpose of his solo trek is different.

Dr Chee, director at the Open Singapore Centre, will be commemorating International Human Rights Day and drawing attention to what he claims are the injustices of Singapore's Internal Security Act (ISA). The non-governmental organisation had intended 30 runners to take part. But the police yesterday refused permission for what was viewed as a "procession-assembly".

Instead, Dr Chee will run the course alone, carrying a letter he hopes to hand deliver to Prime Minister Goh Chok Tong calling on the government to abolish the ISA.

The legislation buttresses the authorities' ability to preserve the tiny country's internal security with a wide range of powers, including detention without trial.

In the first years after independence it was used against suspected communist agitators, but although that threat is seen to have eased, the act remains in place.

The solo run is due to take place three days after Singapore's Senior Minister Lee Kuan Yew accepted the controversial award of an honorary doctorate from the Chinese University and expressed surprise that Hong Kong people seemed less happy after the handover than they were in the colonial era.

With protest and dissent so rare in Singapore, what would be an unremarkable jog in many other countries assumes greater significance. Dr Chee will start at the Whitley Detention Centre, where some ISA detainees are believed to be held, and conclude with a rally in Hong Lim Park, the venue for the recently introduced Speakers Corner - an area where people can publicly express their views after registering with the authorities.

Dr Chee says the event is intended as a wake-up call. "Everything is done in such secrecy that no one really knows how many we have behind bars; how they are treated; whether they are in communication with their families and how basically this whole thing is handled. It is crazy in this day and age, in so-called modern Singapore, to have such laws giving the government such wide-ranging powers to arrest citizens as they please."

Dr Chee, also the secretary-general of the small opposition Singapore Democratic Party, is no stranger to taking on the authorities. In 1998 and 1999, he gave two public speeches without first obtaining the permit required under the Public Entertainment Act. He was fined for both speeches, but opted to serve 19 days in jail rather than pay.

Dr Chee says the rights-day anniversary will not be neglected. "We are marking International Human Rights Day in Singapore in a way that's never been done. December 10 comes and goes and we've never really made a point to draw attention to the abuse of human rights in Singapore."

The government disagrees strongly with the criticisms of Dr Chee and the Open Singapore Centre. It said yesterday that it stood by the act as "a measure of last resort".

A spokesman for the Ministry of Home Affairs said that only one person was presently detained under the ISA - on suspicion of spying.

"The person in question had engaged in espionage activities on behalf of a foreign power," the ministry said in a written reply to questions. "The government has not published his identity because to do so would inflame bilateral relations with the country concerned. The person, however, is not detained secretly; his family members and lawyer, as well as all those involved in the ISA review processes, have access to him and are obviously aware of his identity and his detention."

According to the ministry, the act is used to counter threats to internal security, public order, ethnic relations and essential services.

"These are situations when the government clearly cannot afford to wait and allow such threats to put at risk the collective security of Singaporeans," the statement said. "The government recognises, however, that the ISA is a powerful law and has therefore used it sparingly over the years only as a measure of last resort."

The law gives the minister for home affairs broad discretion to order detention of people deemed to pose a serious threat. The initial detention may be for up to 48 hours, which can then be extended for 28 days if supported by evidence and approved by a police officer holding the rank of at least superintendent. Beyond that, the minister can extend the custody for up to two years if supported by the president.

The ministry said detainees had a right to be informed in writing why they had been taken in and were entitled to a lawyer. However, they had no right to challenge the basis for their detention through the courts. Those held may make their case to an advisory board, headed by a Supreme Court Justice, which makes recommendations to the president. He is under no obligation to comply with the board's findings.

By law, ISA prisoners have their cases reviewed by the board periodically, irrespective of whether they have challenged their detention or not. In addition, a body of inspectors, drawn from a pool of 58 Justices of the Peace, community leaders and "prominent members of the public" make unannounced calls on ISA detainees "to ensure his well-being", the statement said.

According to the United States State Department, which issues an annual survey of human rights conditions around the globe, the ISA has indeed been applied sparingly over recent years.

"No one was detained under the ISA from 1989 through to the end of 1996. Two persons were detained in 1997, and four in 1998, all for alleged espionage. Of these six, two remained in detention at the end of 1998. There were no reports of any new detentions under the ISA during [1999]," the latest survey said.

Dr Chee and the Open Singapore Centre want the ISA removed from the statute book. "We are calling on this Government to abolish the act as well as to apologise to the people that they have detained for such a long time without ever giving them a trial."

The authorities, led by Mr Goh and Senior Minister Mr Lee, are unlikely to comply. They have repeatedly stated that part of Singapore's outstanding economic success and stability has flowed from the country's decision to place the interests of the nation and community ahead of the individual's.

In his memoirs, Mr Lee recounts a meeting in 1978 with Patricia Derian, the then US assistant secretary of state, who urged him to abolish detention without trial.

"I told her that the law was challenged by the opposition at every election and each time an overwhelming majority of the electorate voted for us [the People's Action Party] and for the law," Mr Lee wrote. "I had to deal with communist subversives, against whom it was not possible to get witnesses to testify in open court. If I followed her prescription, Singapore would come to grief."

But Dr Chee says the ISA exerts a pernicious influence over Singapore people whether they are agitating for change or not. "They are terrified of that knock in the middle of the night if they are too vocal against government policy. And this translates into political apathy. It drains away even the energy that's needed, the dynamism, the vibrancy that's needed for the economy that is supposed to be more and more dependent on spontaneity and creativity and innovation."

Such assertions are impossible to verify, and drew a sharp response from the government. "This is a cheap caricature which the Open Singapore Centre has drawn in order to inflate itself and the agenda it shares with its foreign supporters," the statement said.

"One need only be in Singapore for a short time to observe the many letters to the press from members of the public, freely commenting and criticising issues and public policies; the often vigorous debate in parliament by MPs . . . who are freely elected, obviously without fear by Singaporeans."

Tomorrow morning, Dr Chee will publicly make his case. A government response may not be far behind and the city state may be in for one of those "vigorous" debates.

Jake Lloyd-Smith the Post's Singapore correspondent.