By Adam Mynott BBC correspondent in Delhi

The country faced a demographic time bomb and India was the first country to attempt to control population growth.

There are lots of people who haven't heard of the condom

Population expert Usha Rai

Half a century later, the birth rate has been halved, but the massive population is still the number one problem facing India.

With the population still increasing by a figure equal to the entire population of Australia every year, it is accepted India's attempts to stabilise it have already failed.

One billion

Aasthah is nearly two and a half. She lives in the suburbs of Delhi with her parents and grandparents and she is very famous.

When she was born in the year 2000, she became the official one billionth Indian.

2000: A clock counts up to the one billionth person

Despite government attempts to check India's population growth, since Aasthah was born, it has continued its inexorable climb to about I.05bn today.

This has happened most rapidly in areas like the so-called Hindi Belt - the central, predominantly Hindi-speaking states.

In the small town of Dadri in Uttar Pradesh, down an alleyway off the main street and behind some shops, is the home of Mohammed Omar and his wife, Aasiyah Begum.

This couple has not taken the population control message to heart. They have 24 children.

Independence

Aasiyah Begum has given birth to 29 children she thinks, but five have died.

Atal Behari Vajpayee: Hopes to slow the growth

The first child was born shortly after Indian independence in 1947 and they have continued ever since.

She says birth control is against her religion - Islam - and adds: "It's a sin to have an operation. No prayers would be said at my grave when I die. Only people with serious health problems can have operations."

All Mohammed and Aasiyah's children live nearby.

Twenty-four children is exceptional, but large families are commonplace.

No condoms

Population expert Usha Rai says India still lacks a coherent approach to holding back the population explosion and knowledge about basic birth control techniques is woeful.

She says: "There are lots of people who haven't heard of the condom.

All of my children work, and between us we have enough to feed the family. We've got no debts.

Mohammed Omar, father of 24

"I know of a person in Meghalaya who said he'd never heard of condoms, he didn't know how they were used, he didn't know where to get them from. This is a major problem in India."

In Dadri, Mohammed Omar works as a handyman at the local police station, where he is something of a celebrity because he has fathered so many children.

But the local police chief, deputy superintendent Pramud Gupta, says he sees too many large families.

"The main factor is illiteracy, I think. They don't realise what are the consequences behind this. The large number of children, they impose the financial burden on them," says Mr Gupta.

But Mohammed Omar says having more than 20 children has never been a burden to him.

"We've not had any problems. All of my children work, and between us we have enough to feed the family. We've got no debts. We're one big happy family," he says.

But he rejects any suggestion he may give up fatherhood: "Do you think I'm too old or something?" he says.