The problem of India’s “missing girls” has been put under a harsh spotlight by new census data showing the ratio of female to male children at its lowest level since independence in 1947.

According to the latest national headcount, there are now just 914 girls for every 1,000 boys under the age of six, down from a ratio of 927 for every 1,000 a decade ago.

Despite India’s steady economic rise in the past 10 years, the figures show the social bias against having girls remains as strong as ever, with illegal sex-selective abortions facilitated by cheap ultrasound technology.

“The figures should make us think 100 times before we call ourselves citizens of a progressive nation,” said Delhi University social scientist Gitika Vasudev.

India’s sex ratio has been falling continuously since 1961, when it stood at 976 girls for every 1,000 boys, and Dr Vasudev said the latest data was “proof of India’s collective failure” to protect girl children.

The global average is 1,050 girls for every 1,000 boys.

Married women in India face huge pressure to produce male heirs who are seen as breadwinners, family leaders and carers when parents age.

Girls are often viewed as a burden to the family as they require hefty dowries to be married off.

“Measures put in place over the last 40 years have not had any impact on the ratio,” conceded India’s home secretary G.K. Pillai, announcing the need for a “complete” family planning policy review. India has a long history of female infanticide – of girls suffocated, poisoned, drowned or left to die.

More common now, thanks to technological advances, is the abortion of female foetuses, or “female foeticide” – a simple, cheap and difficult to police process with ultrasound tests costing as little as $10.

Signboards at clinics stipulating: “No sex determination tests done here” often pay little more than lip service to the law, and portable ultrasound machines mean tests can be carried out in the most remote villages.