'The question of female foeticide and infanticide is part of our investigation, as is illegal abortions,' said superintendent of police Satish Saxena, hours after the bones were found.

Hundreds of thousands of unwanted baby girls are killed in India every year, either before their birth or shortly afterwards. Last year, research published in British medical journal The Lancet found that 10 million girls had been murdered during the past 20 years.

The result is a chillingly skewed male-female ratio. The number of girls born per 1,000 boys born fell from 945 to 927 between 1991 and 2001, according to the latest Indian census figures. Many districts report as few as 800 girls for every 1,000 boys.

Female infanticide, the murder of a baby girl shortly after her birth, has long occurred in India. Several factors - a deeply ingrained social bias against daughters; the need to pay vast dowries when they wed; and their brothers' greater earning power and tendency to live at home, supporting parents, after marriage - have imperiled the lives of baby girls for centuries.

In the early 19th century, a British soldier, Alexander Walker, recorded his horror at seeing a mother drowning her newborn baby girl in a trough of milk in the western state of Gujarat.

Today, however, girls are more likely to be aborted in the womb than after birth, due to the proliferation of ultrasound machines, which after 14 to 16 weeks of gestation can usually determine the gender of the foetus.

In 1994, the use of such technology to determine the sex of children and abortion on the grounds of gender were banned.

But little is done to enforce the law, which is regularly flouted by doctors. '600 rupees [HK$106] now, save 50,000 rupees later' is a common advertising slogan of diagnostic teams with ultrasound machines. For years, human rights campaigners have been telling the world that the death of so many baby girls amounts to genocide.

And every few years, with wearying regularity, the government seems to acknowledge the crisis. Last year, it launched a campaign known as 'My Strength, My Daughter', which sought to tell parents that killing their daughters was wrong. This year, the launch of a new campaign coincided with the gruesome discovery in Ratlam.

The government last week announced it was setting up a network of 'cradle centres' where parents could deposit unwanted daughters. 'What we are saying to the people is, have your children, don't kill them,' Minister for Women and Child Development Renuka Chowdhury said. 'And if you don't want a girl child, leave her to us.

'It is a matter of international and national shame for us that India, with a growth of nine per cent, still kills its daughters.' Asked whether the scheme would encourage families to abandon their girls, she said: 'It doesn't matter - it's better than killing them.'

Sabu George, who has campaigned against female foeticide and infanticide for two decades, said the latest campaign would not work. 'Girls in India are in the greatest danger in the womb, not when they are born,' he said. 'This is merely a gimmick and it won't have any effect at all.'

A similar scheme, he said, was established in the southern state of Tamil Nadu in the 1990s, where parents were encouraged to leave their infant girls at government hospitals, which are often under-staffed, grim places. Several of the abandoned girls died.

'Absolutely the only way to combat this genocide is to enforce the law over ultrasound machines,' Mr George said. 'Doctors, almost completely unchecked, are making millions of dollars from the death of baby girls.'

The shortage of Indian females, meanwhile, is beginning to affect society. Many young men now have to travel a long way from home to find a bride, often of a lower caste. And in some cases, the tradition of a bride's family paying a dowry to the groom's family is being reversed. Many grooms now pay for the cost of the wedding.

Such changes are unlikely to stop parents wishing the death of their daughters. For many Indians, the economic reasons for wanting more sons than daughters faded many years ago. Today, in modern India, middle-class girls are fast catching up with their brothers and offering as much financial assistance to their parents. But the view that females are inferior persists.

India's middle classes are more likely to abort their daughters than the poor. The Lancet study found that female foeticide was most prevalent among affluent, urban and educated people, who have the easiest access to technology. In some of Delhi's most affluent neighbourhoods there are about 850 girls to every 1,000 boys.

'You will very, very rarely see a prosperous family with more than one daughter,' Mr George said.

Pinki Singh, a marketing executive in Delhi, is pregnant with her first child. Middle class and comfortably off, she knows that whether her baby is a boy or a girl it will have a good education and the chance to earn a decent living. She will not, she says, ask her doctor to tell her the sex of her baby.

'But I hope it's a boy,' she said.