In his reply to the Presidential Address in Rajya Sabha, Prime Minister Narendra Modi today strongly defended government's ban on high denomination currency in November, saying it has no parallel in the world and could even be the subject of a "case study at universities". In the hour-long speech, the Prime Minister also took on the opposition, targetting his predecessor Manmohan Singh in a remark that triggered a walkout by the Congress, which is numerically strong in the upper house. The BJP had issued a whip to its Rajya Sabha members, asking them to remain present for the Prime Minister's address.