The studio audience at the 2012 program gave wrong answers to all three, estimating that around 2 per cent to 10 per cent of children might be sexually abused, saying children were safest in their homes, and that the abusers must be strangers.

The truth, as Khan pointed out before interviewing survivors, was that 53 per cent of all children in India have suffered some form of sexual abuse according to the latest available figures from a 2007 government survey. What was shocking was the survey showed that children are most at risk at home and the culprits are usually male relatives or trusted family friends. Indeed, it found that 31 per cent of sexual assaults were committed by the victim's uncle or male neighbour.

The gasps of incredulity from the audience on hearing these facts were followed by tears as they listened in horror to Khan asking twentysomething Cindrella Prakash to relate how a family friend had regularly assaulted her, starting when she was 12.

''My mother was having dialysis. Those were the days when he knew he would find me alone. I was scared to tell my parents because I thought they might stay at home to protect me instead of going to the hospital for dialysis and my mother would die,'' she told Khan.

His next guest was Harish Iyer, 35, who was sexually abused from the age of 7 to 18 by a close male relative who sodomised him. He invited his friends to abuse Iyer too.

''I distrusted all men. I used to hate standing with my back to people in school in case there was blood on my shorts,'' said Iyer. When he was 12, Iyer plucked up the courage to tell his mother that he was bleeding from his anus. Though loving and close to him, she brushed it aside. ''It's the mangoes you've been eating, they can cause heat in your body,'' she said.

The 2007 survey showed that 53 per cent of the of 12,500 children interviewed had been sexually abused in ways that ranged from severe - rape or fondling - to milder forms such as forcible kissing.

Shockingly, despite widespread media coverage when the survey was released, public reaction to the results faded quickly, and the response from authorities was almost non-existent. According to many who work in the field of child abuse in India, most Indians continued to think that they love and indulge their children, that most families are happy, and that such perversions as child sex abuse, including incest, belong to the sex-obsessed West.

In devoting an episode of his series to incest, Khan broke new ground. His intention was to shatter both the delusion that it doesn't affect Indian families and the code of silence around the terrible problem.

''India has 470 million children. If 53 per cent of the 12,500 children interviewed were sexually abused, then this is the greatest silent epidemic in the country,'' says Suchismita Bose, director of The Foundation, a Mumbai NGO.

Child sex abuse is not peculiar to India. As in other countries, in India it is found in every social class and while it also affects boys, it is primarily girls who are the victims.

Yet, the figures available for India are appallingly high. Anuja Gupta, director of RAHI (Recovering and Healing from Incest), a Delhi support centre for victims, says that while the 2007 survey may not be as rigorous as some studies, it revealed that the problem of incest was widespread.

''From the 2007 figures, I'm not sure you can say that one in two Indian children suffers sexual abuse. One in two of the children in the sample were abused. Unlike in the West where rigorous and conclusive data collected over a long period is available, we don't have that. But yes, in my 18 years' experience, I have met very few women who have not been abused in some way,'' says Gupta,

Experts believe that in India, certain cultural and social factors might play a part in making abuse easier and speaking out about it harder.

These factors include a taboo on talking about sex and sexuality; entrenched patriarchy and misogyny in large parts of society which serve to make women powerless and vulnerable; the belief inculcated in children that elders are right and must be obeyed; and stigmatisation of the victim and family by their entire social circle.

Khan's TV program opened the floodgates. At the government-funded Childline India Foundation, which runs a 24-hour helpline in Delhi and other cities, Heenu Singh, head of the northern region, saw a spike in the number of calls after the program was aired. ''Children realised they were not alone, that others too had been abused,'' she says.

Singh remembers a case from that time which exemplifies the complex factors that come into play if children are able to tell an adult that they are being abused. The young woman who called the helpline said her father had been having intercourse with her for five years.

Finally, she told her mother. The mother protected her two younger daughters by sending them to live with her parents. But she left the eldest at home. ''She told her daughter to tolerate it, until she got married and could leave,'' says Singh.

The situation became more distressing after the young woman decided, after much agonising, to report her father to the police.

''The father was arrested and the victim taken to a residential home. Her mother is struggling to support her two other daughters. Both sides of the family have abandoned them. No one will want to marry these three sisters. That's why children take so long to speak out. The consequences are so catastrophic for everyone,'' says Singh.

The cultural inhibition against talking about sex and sexuality is something that everyone working with survivors singles out as being particularly harmful. Indians are uncomfortable talking about sexuality. Sex education in schools is frowned on, with opponents calling it ''indecent''. Menstruation is a forbidden topic.

''We need open conversations about sex so that children understand what is normal sexual contact and what is abnormal, but we can't do that while sex is shrouded in shame and mysticism,'' says Vidya Reddy, director of Tulir, one of the country's largest groups working to prevent abuse and to counsel victims.

''Some girls don't even realise they are being sexually exploited because they have no knowledge or experience. More conversations would also enable parents to detect abuse by being more aware,'' says Reddy.

Pooja Taparia, a graphic designer by profession, set up the organisation Arpan in Mumbai in 2006 after watching a play on child sex abuse and discovering that only two NGOs were working in this field.

Arpan has worked with 66,000 children. Taparia says the reluctance to talk about sex and private body parts has not changed. The standard cry of family members, when young children inadvertently touch or expose their genitals, is ''shame, shame!''

When this inhibition about talking about sex is added to the shame and guilt that victims already feel, it is a miracle that any child in India ever speaks out.

''Very early on, children realise that sexuality is stigmatised. If body parts are treated as something dirty, an abused child is going to be unwilling to raise the topic. No one even uses the right vocabulary for body parts, preferring euphemisms like 'man point' or 'pee pee' for penis,'' says Taparia.

Despite the advances made by educated and affluent women, the vast majority of Indian women are subservient. They are not the decision-makers or breadwinners and must defer to the men in their lives.

Consequently, if a mother discovers that her husband, cousin, male relative or family friend is abusing her child, she is often not confident enough to speak out. Doing so can leave her and her children destitute.

''One of my cases was an orphan living with her grandparents,'' says Taparia.

''Her grandfather had sex with her for years and later invited his neighbour to rape her too. The grandmother knew but kept quiet, fearing the financial cataclysm if the breadwinner was put behind bars.''

Alongside lack of economic independence, the fear of destroying the family name holds many women back. Girls and women are taught that they must protect the family name no matter what. In Indian society, people are not individuals but part of a collective unit and any ''shame'' that attaches to one person stains the entire family.

Gupta says the very size of the extended Indian family also provides more opportunities for abuse to happen. The extended family in India can include a father's fifth cousin; he is not regarded as a distant relative but very much an integral part of the family.

''Family is paramount. Life revolves around relatives. Holidays are spent with relatives. So, with male cousins, grandfathers and their brothers, brothers in law, and uncles, there are more opportunities for potential abusers, particularly as all relatives are regarded as close,'' Gupta says.

Some of the worst abuse happens in residential care facilities where inspections are infrequent. Some facilities are not even registered. On May 29, The Times of India reported the arrest of Ajit Dabholkar, who ran an illegal shelter just 60 kilometres from Mumbai.

The children at the shelter, some as young as 11, reported being forced to have sex with Dabholkar and with one another. The abuse came to light when one girl visited her home in early May. She told the police that if they resisted, they were forced to eat dog excreta and locked up.

Perhaps the most powerful deterrent in speaking out about abuse is the cruelty of Indian society. Victims know that they and their loved ones will be shunned like diseased street dogs.

The parents of a 16-year-old girl in Kerala experienced this from the day their ordeal began. In 1996, their daughter was raped for 40 days by 42 men who drove her from place to place. The case involved top politicians and dragged on for years. Last year, 35 of the accused were finally convicted.

But in all those years, it was not the accused but the girl and her parents who were ostracised. Every few months, when their identity became known, they were forced to move out by hissing, disdainful neighbours.

Very gradually, the culture of silence is being broken. In April, actress Kalki Koechlin said publicly that she had been abused as a child. As it happens, Koechlin has recently separated from her husband, film director Anurag Kashyap, who also revealed that he was abused for 11 years.

Last year, Anoushka Shankar, musician and daughter of the legendary Indian sitar player Ravi Shankar, admitted she had been subjected to groping as a little girl by a man her parents trusted. Such admissions were unthinkable till very recently, and suggest there is some progress in breaking down the taboo around sexual abuse and incest.

In recent years, many NGOs have been set up to help victims by , for example, conducting workshops in schools and raising public awareness. Many have also lobbied the government for better policies.

This lobbying, added to the slight increase in society's willingness to talk about the issue, has led to the formation of a new law dealing specifically with child sex abuse. The 2012 Protection of Children from Sexual Offences law provides protection to all children under the age of 18 from sexual abuse.

The new law is different from those that already existed to deal with sexual abuse in that it deals specifically with children. Penalties range from three to 10-year jail sentences.

Singh says high-profile cases such as the 2012 Delhi gang rape, in which a young woman was raped so savagely that she died of her injuries, have also added to the push towards breaking the silence around incest.

''After the Delhi gang rape, rape is now openly discussed. I hope child sex abuse will be given similar treatment. Only when the silence is broken can we start confronting the conditions that allow it to happen.'' .

Amrit Dhillon is a journalist based in Delhi.