India, June 25 -- The Opposition on Thursday stepped up its attack on the Centre over the ministry of external affairs' (MEA) assertion that a passport is primarily a travel document and not conclusive proof of citizenship, questioning what documents Indians can rely on to establish their nationality.

The criticism came even as the government insisted there was nothing new about its position and said the legal understanding of passports and citizenship has existed for decades.

Congress leader Supriya Shrinate questioned the government's stance, asking what document citizens should treat as proof of nationality if passports, Aadhaar cards, PAN cards and voter IDs are all deemed insufficient.

"The Modi government says that a passport is ...