New Delhi, Feb 18 (IANS): Several opposition MPs on Tuesday grilled Union Home Secretary Ajay Kumar Bhalla over additional columns in the National Population Register (NPR) questionnaire during a meeting of the department related standing committee on Home.

The NPR, which is set to take off on April 1 to enumerate usual residents of the country, has evoked large scale controversy as the government has inserted certain addition questions in the format including date and place of birth of individuals' parents.

Sources said, during the deliberations on the allocation of fund for conducting NPR and Census exercise in the budget, opposition members asked the Home Ministry officials the reasons for changing the NPR questionnaire vis-a-vis 2010, when the exercise was first conducted in the country.

"No reasonable answer was provided by them except that the additional questions are optional and people are free not to answer them," a source said.

Asked "will not such persons be marked for not offering the answers on contentious questions", the source said: "The officials said, they will not be marked. But we contended that the exercise may turn out to be a prelude to preparing National Register of Indian Citizens (NRIC). On this they had no answer to offer."