A doctor and his assistant have each been jailed for two years in India for using ultrasound scans for sex-selective abortions.

Dr Anil Sabsani, a radiologist, and his assistant, who was not named, were trapped in the northern state of Haryana after the authorities were told that his clinic was offering illegal sex-determination tests.

Dr Sabsani told a pregnant woman sent in undercover that he would reveal the sex of her child for an additional fee of 1,500 rupees (�20).

After the woman paid the money, Dr Sabsani was caught on a hidden video camera confirming that the unborn child was female, saying: "But that can be taken care of."

Doctors and social activists welcomed the convictions, the first in India, as a breakthrough in the fight against the practice that accounts for the death of up to 500,000 female foetuses every year.

Passing judgment, the court in Palwal said: "Because of the illegal acts of people such as Dr Sabsani, the sex ratio is declining day by day."

Indian census figures show that male-female sex ratios have been declining steadily from 945 females per 1,000 males in 1991 to 927 per thousand in 2001.

In some parts of Haryana and the Punjab, where the killing of female foetuses is especially rife, the ratio is as low as 800 girls per 1,000 boys, leading to a chronic shortage of brides and other social ills.

Female infanticide has been widespread for centuries, particularly in northern India, where girls were considered a financial liability because they were unable to do manual labour and required an expensive dowry.

In modern times, infanticide has been largely replaced by foeticide because of the availability of legalised abortion and affordable ultrasound clinics.

Studies have shown that female foeticide is most prevalent among affluent, urban and educated populations which have the easiest access to such technology.

A report in The Lancet in January estimated that 10 million female foetuses had been aborted in India in the past 20 years.

The potential impact of ultrasound machines on sex ratios was dramatically illustrated by figures obtained by a European Commission technical adviser on a recent visit to the mountainous state of Uttaranchal.

Birth records at a clinic in the village of Jahkoli showed that 38 females and 44 males had been born in the year 2004-5, about average for India as a whole.

However, in 2005-6, after an ultrasound machine was installed in the nearby town of Rudraprayag, the birth register in Jahkoli showed 61 deliveries, of which only 14, or 22 per cent, were girls.

Dr Vinay Agarwal, the president of the Indian Medical Association, described Dr Sabsani's conviction as "historic".

He said: "The medical profession is doing all it can to address this social evil. People should be proud to have a girl child."