Addressing a conference of data users of the 2001 census, Advani admitted that there was criticism of the scheme from several quarters. The home minister said the card was not intended just to identify illegal immigrants, but also to resolve numerous day-to-day problems faced by the people.

He said the citizens' identity cards will also help in the census operation.

The cards are expected to carry details like name, date of birth and residence of the holder.

Advani said India was among the very few countries where the citizens did not have a document to identify themselves. This led to several problems, he said.

As a parliamentarian he was often approached by people who wanted certificates of age or caste for getting old age pension or other benefits from the government, the Union Home Minister said. At times, he did nothave enough proof to certify that the person who approached him was old enough for the pension.

The two-day conference of data users of the 2001 census, inaugurated by Advani, is meant to prepare for the next once-in-a-decade census, which has been billed as the Millennium Census. It would be the 14th in an uninterrupted series.

The Indian population is expected to have crossed the one billion mark when the next census exercise begins. About 20 lakh enumerators would be deployed by the Government for the census exercise: the figure is more than that of the entire adult population of a country like Singapore.