Manoubia Bouazizi has grown used to the idea that her son Mohamed no longer belongs to her but to the Arab world. In the streets near where she lives on the outskirts of Tunis, she is stopped by people who recognise her, who have heard she is the mother of the market trader who set himself on fire in protest against an authoritarian regime, who kick-started the Jasmine revolution, and so the Arab spring.

His likeness is everywhere. Around the corner from her home, a pizza restaurant proprietor has mounted a full-colour reproduction of Mohamed's face in his window to advertise a special discounted "Revolutionary Menu".

Manoubia freely admits she, also, has made money from the global interest surrounding her son's death. Sometimes she will be paid by the media organisations who want to interview her, and she has a ready-made contract drawn up for them to sign. The family were given 20,000 Tunisian dinars (about £9,000) by former president Zine al-Abidine Ben Ali as compensation for their loss and there are rumours – which Manoubia denies – that she has sold Mohamed's vegetable cart to a rich businessman in the Emirates.

Still, her new-found prosperity is much in evidence. The Bouazizi family used to live in a modest, concrete house in the central Tunisian town of Sidi Bouzid. Now Manoubia, her husband and her six surviving children have decamped to a large apartment in La Marsa, a pretty seaside suburb of Tunis. Inside, there are caged canaries hanging from the tiled walls and a computer in one of the bedrooms.

When asked to describe what kind of person her son was, Manoubia has difficulty replying. "I can't think of one single memory," she says. "He was a man of good faith." When pressed, her daughter Laila remembers that her brother's favourite meal was "steak and chips" and that he supported Esperance Sportive, a Tunisian football team. Other than this, the family is disinclined to dwell on personal detail.

For Manoubia, as for those around her, it seems that the man has been subsumed by the myth. "It is strange to think that my little Mohamed should grow up to become this person," Manoubia says, sitting in the front room of her rented house, her black robes gathered around her and set starkly against a bright orange blanket covering the sofa. She turns away as she speaks, not making eye contact, and it feels sometimes as though she is reciting answers she has learned by rote, having formulated the sentences hundreds of times before. "I am proud and happy that he should have been the first spark of the revolution."

It is a phrase I will hear again and again, in varying forms across Tunisia. Some will call Mohamed Bouazizi "the drop that tipped over the vase"; others will insist that his death "lit the touchpaper" for the Arab spring revolts. But listen closely and there is also a growing murmur of dissent among those who believe that Mohamed was not a political hero but a media creation, manufactured by a myth-making machine that swung into action in the immediate aftermath of his death.

I had gone to Tunisia with Observer photographer Andy Hall expecting to tell the story of a nation unified behind an ordinary man who provoked an extraordinary set of events across North Africa and the Middle East. Instead, to our astonishment, we discovered a tale of bitter feuding and division in his hometown of Sidi Bouzid, where the truth of what happened is disputed by rival factions and where the once-glorious memory of Mohamed Bouazizi is picked over like carrion in the streets.

"His mother is the only winner of this revolution," says Hania Bouazizi, a cousin of the family and Manoubia's former neighbour. "Life is still hard for the majority of Tunisians, but she has banked thousands of dinars. She became so greedy, so haughty – she'd go into supermarkets and say, 'Don't you know who I am? I'm the mother of the martyr Mohamed.' She became narcissistic and wanted to take everything for herself… That's the real story."

Hania's sentiments, though venomous, are shared by several other Sidi Bouzid residents, none of whom wishes to put their name on record in case they exacerbate an already febrile atmosphere. But the whispers point to the growing belief that the romantic narrative of the martyrdom of Mohamed Bouazizi is perhaps not all that it seems.

The facts are that on 17 December last year, Mohamed, a market trader whose father had died when he was three and who had been helping to support his family financially since the age of 10, set himself on fire after a dispute with a government official over where he could sell his fruit and vegetables. At the time, it was widely reported that the municipal inspector, a woman named Fedia Hamdi with a reputation for strictness, had slapped Mohamed across the face – the ultimate insult in such a patriarchal Arab community. The confrontation seemed to pit an ordinary man, struggling to make a living, against the uniformed symbol of a corrupt regime. Bouazizi's suicide at the age of 26 was seen by many as an act borne of his intense frustration with authoritarian rule. It became the domino that fell and triggered a chain of revolutions across the Arab world.

In Sidi Bouzid, a Tunisian town of 70,000 inhabitants 300km from the capital Tunis, crowds gathered outside the governor's offices chanting slogans against a dictatorial state that so humiliated its citizens. Some claimed – incorrectly – that Bouazizi had been a university graduate unable to seek work, a slogan that fitted neatly with the rising problem of youth unemployment in the region. People took to the streets in droves, spraying graffiti across the white walls of government buildings, recording events on their mobile phones and uploading the videos on Facebook in defiance of the 23-year rule of President Ben Ali.

On 18 December, 2,000 police were sent to quell the riots, resulting in two civilian deaths. But the revolt continued to gather momentum, spreading to the surrounding towns and cities and climaxing in Tunis, where students congregated in front of the prime minister's official residence in Kasbah Square to make their voices heard. They protested against myriad injustices: a lack of freedom of speech, rising unemployment, spiralling food prices and the regime's endemic corruption. Under Ben Ali's rule, bribes were paid as a matter of course, corruption was rife and the president's family lived a life of ruthless extravagance to the cost of the Tunisian people.

Mohamed Bouazizi had not been alone in his desperation. "Tunisia was run like a mafia state," explains Alibi Rohidi, 50, a teaching assistant from Meknassy, a town 50km from Sidi Bouzid where the walls are painted with striking revolutionary murals. "Ben Ali stole from his people. There was a total absence of democracy. He dominated with an iron fist."

On 14 January, 28 days after Bouazizi's self-immolation, the president fled to Saudi Arabia. Tunisia was free. And all, it seemed, because of the fateful slap that had finally pushed a humble market trader over the edge. Except that, according to the municipal inspector at the centre of the controversy, the slap was a fabrication. In Fedia Hamdi's eyes, the Jasmine revolution was founded on a lie.

Fedia Hamdi is a slight, stooping woman who looks older than her 46 years. She moves with the exaggerated caution of an elderly lady, as though afraid of tripping. Until recently, the only image of Hamdi in circulation was a photograph taken for work: it showed a pretty, oval face with kohl-ringed eyes, peeping out from beneath the light blue cap of her official uniform. When she walks into the front room of her parents' comfortable home in Meknassy, the change in her physical appearance is so marked that at first I do not recognise her.

Her frailty is, she explains, largely due to her time in prison. After the fracas with Bouazizi, an internal investigation by the municipal authorities exonerated her from all wrongdoing. In spite of this, she was arrested on the orders of Ben Ali on 28 December in his last-ditch attempt to pacify the rioters. "I feel I was a scapegoat," she says now. "I would never have hit him [Bouazizi]. It was impossible because I am a woman, first of all, and I live in a traditionally Arab community which bans a woman from hitting a man. And, secondly, I was frightened… I was only doing my job."

After a short period of house arrest, Hamdi spent almost four months in a prison for civil offences in nearby Gafsa despite continuing to protest her innocence. In jail, she went on hunger strike for 15 days before doctors intervened. "I was sick," she explains. "For one month, I didn't reveal my identity to the other prisoners because I was so scared of what they would do to me."

But after Ben Ali had fled the country, the tide began to turn. In February, a Tunisian TV station revealed that Bouazizi's mother and stepfather had accepted money from the president, despite having previously denied this. Hamdi felt safe enough to tell her fellow prisoners who she was. Instead of shunning her, they expressed their support. Outside the cell door, Hamdi's former colleagues set up a Facebook group campaigning for her release.

"It became a story of a political prisoner," says Alibi Rohidi. "In cafés, people would gather and say to each other that Fedia had been wrongly imprisoned by the president, that he had made an example of her. But we never said it in public because we did not want to endanger the revolution."

There was a sense, too, that after 23 years of being unable to speak freely the Tunisian people found it difficult to change the habit. "Tunisians are used to living their life in fear," explains Asma Gharbi, an engineer from Sidi Bouzid. "If you spoke out about something that didn't seem right under Ben Ali, you would be removed. You get used to not speaking out, even if you know something is wrong, and that mindset takes time to change."

But once the revolution had achieved its aims and Ben Ali had gone, Rohidi says the atmosphere in the region changed. The terror began to dissipate. "People started to understand the whole story [of Hamdi and Bouazizi], and said they wanted reconciliation."

Encouraged by the shift in local opinion, Hamdi's family approached the lawyer Basma Mnasri to investigate a possible legal defence. Mnasri, a formidable woman sporting glamorous wraparound sunglasses, says she was "convinced of Fedia's innocence… Mohamed Bouazizi was let down by the system. But Fedia is the second face of injustice in Tunisia."

On 19 April, after 111 days of incarceration, Hamdi was finally freed by a tribunal in Sidi Bouzid after Mnasri demolished the case against her. She was found innocent of all charges when it emerged in court that only a single person claimed to have seen the slap – a street trader who bore a grudge against her – while four new witnesses testified that there had been no physical confrontation.

Hamdi had not seen her mother for four months. On the day of her release, the two women hugged each other on the courtroom steps, unable to speak through their tears. "My family and my colleagues suffered much more [than me] because they were rejected by the community," says Hamdi. "They tried to tell their story but no one would listen… In prison, I missed my family so much. When I saw them again after I was freed, I felt newborn."

We meet two DAYS after Hamdi's release in a room filled with a garrulous gathering of her colleagues and her seven siblings, who have come to celebrate her release over cups of sweet, milky coffee. Tahar Hamdi, her 75-year-old father and a retired police inspector, sits to one side wearing gold-rimmed spectacles, a red Fez and a three-piece suit. His wife, Meriem, 74, holds a "sebha" in her hands – a string of white beads that is the Islamic equivalent of a rosary – and prays under her breath. "It was unbearable having her in prison," Tahar says. "I hadn't cried since the death of my mother in 1998, but since my daughter was arrested, I cried so much I thought I'd never stop. She is such a loving girl. Even as a child, she always had a strong sense of right and wrong."

I am the first journalist Hamdi has ever spoken to. Why has she kept silent until now? She seems to find the question surprising. "You are the first to have listened," she replies, tears falling down her cheeks. She clasps her hands together to stop them from trembling. "It made me sick to my heart that everyone refused to listen. I felt I was facing so much injustice."

Hamdi's version of events differs from that of the Bouazizi family in small but crucial ways. She acknowledges that there was a confrontation with Mohamed at about 11am on the morning of 17 December because he had parked his fruit and vegetable cart opposite the municipal buildings and "the law doesn't allow market traders to go in a public zone". But she insists she never slapped him. A small crowd of market traders had gathered around her and she says she was scared that the dispute could get out of hand: "When I asked him to leave, he refused and he grabbed hold of my hand, hurting my finger. He was angry with me, so I let it go, but as a penalty I confiscated some of his bananas and peppers and gave them to a charitable association. Afterwards, I went back to my work and then I went home at 1pm."

Hamdi says Bouazizi was "hysterical" when she left. "He was almost unaware of what he was doing." The market trader went first to the police station to try to retrieve his confiscated goods, but was turned away. He then asked to see the governor and was turned away again. Perhaps, at this stage, the accumulated frustrations and humiliations of the preceding hours started to bubble over. Whatever the cause, Bouazizi decided to pour flammable fluid – possibly paint thinner or petrol – over his body shortly after 1pm and then set himself alight.

Did he know what he was doing? Even that is a source of contention. One resident of Sidi Bouzid claims that he poured the liquid over himself merely "as a threat. He didn't mean to kill himself". Several of Hamdi's colleagues even suggest Bouazizi set himself on fire by accident while lighting a cigarette.

Bouazizi was taken to a hospital 100km away in Sfax that could cope with the extent of his injuries. Later, when President Ben Ali took a personal interest, he was placed under the care of a medical team in Tunis. In a vain attempt to deflect the gathering criticism of his handling of events, the president visited a heavily bandaged Bouazizi in hospital on 28 December. He was said to have died a week later, on 4 January. Even this is disputed.

A handful of people I speak to insist there is anecdotal evidence to suggest that Bouazizi died within 24 hours of admission. "His burns were so bad he could not have survived any longer than that," says Shali Dhafer, a lawyer in Sidi Bouzid who took part in the first anti-government protests. "I saw him when he got taken into the ambulance: his legs and arms were stuck together as if his skin had melted, and he was black all over. But the government said he died on 4 January. Why? It was a piece of theatre. The president wanted to be seen visiting the martyr. It was one of his biggest tricks and lies. He was an expert in dishonour."

Whatever the sad truth of Bouazizi's death, it seems there are some in Sidi Bouzid who are determined to erase the memory of his life altogether. In the aftermath of his self-immolation, a series of impromptu memorials featuring Mohamed's photograph sprang up across town. A plaque was put up in the central square, renaming it the "Place de Mohamed Bouazizi". But the morning after Hamdi was released from jail, residents awoke to find that every single image of Mohamed had been taken down and every piece of graffiti bearing his name had been painted over. The plaque in the central square had disappeared. It is as though, having been robbed of the narrative they so fervently wished to be true, there are those who want quite literally to whitewash over the blemished past.

"Everyone was so impressed by the revolution," says Asma Gharbi. "We thought he was a hero, but the reality is completely different. Now, we feel shocked and are struggling to come to terms with it all."

In La Marsa, Manoubia Bouazizi is determined to cling to her role as the martyr's mother. Her children also wish to keep their brother's memory alive: her two teenage daughters, Samia and Basma, now use images of Mohamed as mobile phone screensavers. Manoubia condemns the residents of Sidi Bouzid who have "taken sides" with Fedia Hamdi as "hypocrites" and directs much of her anger towards the Hamdi family, at one point alleging that they have been paying court witnesses to claim the slap never happened. For their part, the Hamdi family wishes to move on. "We have no problem with the Bouazizis," says Tahar Hamdi. "If they came to visit, we'd be as hospitable as we are with anyone."

And although the genesis of the revolution is now disputed, the end result is widely acknowledged as a positive one. The subsequent fallout might have degenerated into an internecine squabble, but the general feeling, as expressed by Shali Dhafer, seems to be that: "The revolution was bigger than two people." After the long years of oppression – of being unable to speak freely, of struggling to make an honest living amid a tangle of corruption and bribery – Tunisians are undoubtedly revelling in the rosy dawn of a new, liberated nation.

Even Hamdi says she welcomes the deposition of the former president and her unwitting part in his downfall. "I am happy about the revolution," she says. "I am a religious woman. All that happened was so hard, but it was my destiny and I am proud of my destiny. It was given to me by God."

The majority of Tunisians I speak to are intensely relieved to have emerged from the long shadow cast by the dismantling of Ben Ali's two-decade dictatorship. Democratic elections are to be held in July.

But, beyond the nobility of the abstract, on a day-to-day level not that much seems to have changed. On the dusty, sun-streaked streets of Sidi Bouzid, the market traders continue to sell their wares. Underneath a stretch of lotus trees, a few metres from where Mohamed Bouazizi killed himself, men with weathered faces set out gleaming piles of peppers, oranges and strawberries. "It's the same as always," says Faycal Neji, a 30-year-old stallholder. "Nothing has changed. It's still hard to make a living. Prices have gone up, but the sale price for our goods has stayed the same. What we have gained is that we are free of fear. We can express our opinions openly."

But then he remembers that there is one, practical thing that has also changed for the better. "We can park our carts here now," he says, gesturing towards the municipal buildings on the other side of the street. "It's illegal, but since the revolution, no one bothers us."

And for that, indisputably, Faycal Neji can be grateful to his fellow market trader, the martyr of Sidi Bouzid.