Since his release without charge from Guantánamo Bay in 2005, Mamdouh Habib has participated in the "Torture Victims Speak Out!" lecture series organised by the National Union of Students. He came to Monash University in Melbourne in September. The small lecture theatre was packed to capacity, but only those in the know were there – the posters advertising his appearance had been torn down within hours of their appearance on university noticeboards. He was dressed in a neat blue suit and was comfortable in front of the audience. His wide-ranging speech included commentary on the War on Terror and the practice of torture in US-run prisons around the world.

Habib had just received the news that he was to be sent home from Guantánamo Bay after more than three years of confinement. As he made his preparations for the journey, he was surprised to find the guards shackling him. He told them, "I'm not charged with anything, and I've been here for years, and now you are releasing me. What do you think I'm going to do to you now?" He reports that the guards replied, "If your hands are free, you could attack us." Habib retorted, "If my hands were free, I would not attack you, because that would make you happy. Instead, I'm going to use my tongue to tell people what you are".

Habib clearly recognises that the most powerful thing that former Guantánamo Bay detainees can do is to speak publicly and critically about their experiences. The media is awash with words about them, but rarely hears words from them. And no wonder. Such stories directly contradict the moral premise of the War on Terror, which is precariously balanced on the idea that the United States and its allies are only ever the victims of aggressive or egregious conduct, and never themselves the perpetrators.

Few in Australia want Habib to tell his story. Former Opposition leader Kim Beazley opposed his request to address a Senate Committee about his experiences in Guantánamo Bay. The former education minister Brendan Nelson condemned a university for permitting him to speak to students about what had happened to him. Three men in Sydney stabbed him outside his home with the words, "You'd better keep quiet". Not long after this attack, a man approached him in a local shopping centre and told him that if he should write a book about his experiences, he would be killed.

This is clearly a man possessed of dangerous words. What is it precisely that people don't want him to talk about? The answer appears to be torture. Since his return to Australia in January 2005, Habib has repeatedly testified to multiple experiences of torture (including on 60 Minutes, Dateline, Insight and Four Corners). Arrested as a terrorist suspect in October 2001 and then interrogated in Pakistan, Egypt and finally Guantánamo Bay, Habib registered complaints of torture in each location from as early as December 2001 in letters to his family and reports to the Red Cross. He reports that while he was in Egypt, he was beaten, threatened with dogs and cattle-prods, suspended from hooks while balanced on an electrified metal drum, and confined to a room that was filled with water up to his chin. He was also shown photographs of his family with pictures of animals superimposed over their faces, and told that they had been killed.

The Coalition government refused to establish an independent inquiry into these claims. To date, they have relied on the results of investigations conducted by the US Department of Defence and the US Navy. Consider, for example, the foreign minister Alexander Downer's response to the question of whether he was concerned about Habib's claims that he had been stripped, beaten and humiliated while in US custody: "Well, the Americans tell us that none of these things have happened". (ABC Radio, May 12, 2004).

But where does this leave the words of an Australian citizen who says he was tortured? Habib's testimony is left here as a painful residue, deprived of both acknowledgement and independent investigation. But what he says is nonetheless so important that we must listen to him.

We need to get to the bottom of Habib's words because he has consistently claimed that an Australian official was present during at least one of his interrogation sessions, a claim which the Coalition government denied. Habib also insists that his Egyptian interrogators relied on information that ASIO officers had taken from his house in Sydney. As a recent investigation by ABC's Four Corners (June 11 2007) indicated, this all raises deeply disturbing questions. The Coalition government repeatedly said that it could not confirm that Habib was in Egypt. Four Corners revealed documents that suggest otherwise. By 19 November 2001, it is clear that officers of the Australian Federal Police and the Department of Foreign Affairs and Trade knew exactly where he was. But what did they do with this knowledge? Egypt is notorious in the international community for its use of more than seventy forms of torture. If the Coalition government knew that an Australian citizen had been rendered to Egypt by the United States, then it should have rung alarm bells. It is terrifying to think that they did nothing.

Even more troubling than this inaction are the official attempts to discredit his words. Habib appeared on Channel Nine's 60 Minutes program on February 13, 2005, immediately after his return to Australia. He provided a detailed account of the various modes of torture that he suffered, particularly while held in Egypt. Despite the deeply shocking nature of his claims, they received almost no attention at all in the Australian media. Instead, the focus was on ostensible omissions in his interview, including, for example, his refusal to divulge his reasons for his visit to Afghanistan. This was characterised by various commentators as a "massive evasion".

However, some officials did address the issue of the torture claims. The response of the former ASIO Director General two days after Habib's interview is exemplary here. In the context of Habib's testimony on 60 Minutes, Mr Richardson made the following statement regarding the claims of torture that Habib had made to the Australian Federal Police in 2001: "His claims of torture lack credibility. We didn't consider that they needed to be considered and investigated – we believed they were humbug and we would consider them humbug if he were to raise them again today" (ABC News, February 15, 2005).

For Richardson, Habib is literally incapable of testifying to torture. Any words he utters on the subject will be "humbug" – a hoax, a fraud, a sham, a deception, a pretence. There is literally nothing he can say, no sign he can emit, which will be testable, credible, or truthful. Foreign minister Alexander Downer continued this effort to undermine Habib's testimony. The day after the 60 Minutes interview, Downer remarked on 2UE Radio that Habib had explained that he had confessed to various crimes because he was being tortured "but then remember we have no evidence except his own claims, the claims of somebody who allegedly has been involved with Al Qaeda – that he was subjected to torture".

So all we have is Habib's words – words that are well on the way to being disqualified. Despite these attempts to discredit him, Habib continues to testify to what happened to him. In his current litigation before the Federal Court, Habib is accusing government officials of complicity in his kidnap, false imprisonment, rendition and torture. The Coalition government tried to have his case struck out. The cruelty of these attempts to block judicial scrutiny of his case cannot be overstated. Torture itself attacks the voice, by breaking it into incoherent sounds of pain or forcing it into the artificial shapes of so-called "confession". A key aspect in any torture survivor's recovery is the ability to tell their story and have it acknowledged. Official efforts to stop this process attempt to deprive Habib of the chance to receive that recognition.

We will only get to the bottom of Mamdouh Habib's dangerous words with a public, independent inquiry into his claims, such as that conducted by the Canadian government in the case of Maher Arar. Arar was tortured for a year in Syria after being taken into US custody in New York on his way home from a family holiday in Tunisia. He was beaten, interrogated and made to sign false confessions, after a long confinement in a cell that he described as a "grave". Arar received compensation and an apology from the Canadian government, and public acknowledgement of the crimes committed against him. Habib deserves the benefit of a similarly transparent process. And so do we. Were Australian officials complicit in the torture of a fellow citizen? If our civil society is to have any integrity at all, we have to know the answer to this question.

For all of these reasons, we must not turn away when Mamdouh Habib talks about torture. His words must not fall on deaf ears.

Dr Nina Philadelphoff-Puren is a lecturer at Monash University.