The NPR, which will be carried out under the aegis of the Registrar General and ex-Officio Census Commissioner of the country, is expected to create a comprehensive database containing particulars of the identity of every "usual resident" in the country. This database will contain demographic and certain other particulars.

The NPR exercise will be carried out for all states and Union Territories, along with the house-listing phase of the census, except in Assam. The northeastern state has been excluded because a National Register of Citizens (NRC) exercise has already been carried out there.

Addressing the media at a briefing this evening, Union Minister Prakash Javadekar said there was no link between the NPR and the National Register of Citizens (NRC) exercise carried out in Assam earlier this year and excluded 19 lakh people from the final list.

"It will not be a long form. There will be a mobile app... It is self-declaration. No document is required. No proof is required. No biometric is required. This is already accepted by all states. All the states have already notified it," Mr Javadekar said.

Demographic details required will include your name and the names of your parents and that of your spouse, as well as basic information like sex, date of birth, place of birth, nationality (as declared), permanent and current address (if they differ) duration of stay at present address, occupation and educational qualifications.

In 2000, under the NDA government headed by former Prime Minister Atal Bihari Vajpayee, the Kargil Review Committee recommended compulsory registration of citizens and non-citizens. The recommendations were accepted in 2001 and the 2003 Citizenship (Registration and Issue of National Identity Cards) Rules was passed.

Previously conducted in 2010 and 2015, the NPR was first authorised in 2004 by the UPA government after an amendment to the 1955 Citizenship Act. The amendment allowed the centre to "compulsorily register every citizen of India and issue (a) national identity card".

Between 2003 and 2009 a pilot project was implemented in select border areas. Over the next two years (2009-2011) NPR was also carried out in coastal areas - it was used to enhance security after the Mumbai attacks - and Resident Identity Cards were issued to nearly 66 lakh residents.

The exercise has been described as a routine process meant to supplement the forthcoming Census and help improve delivery of benefits from the government's various welfare schemes. The data will also be provided to state governments