Union Health and Family Welfare Minister Jagat Prakash Nadda on Monday asked Himachal Pradesh Chief Minister Virbhadra Singh to immediately resign on moral grounds in the wake of corruption allegations against him.In a statement here, Nadda said it was a matter of surprise that the Congress leadership in Delhi was totally silent on the issue of disproportionate assets and money laundering cases against Virbhadra Singh by the CBI and the Enforcement Directorate."This silence of Congress president Sonia Gandhi and vice president Rahul Gandhi on corruption allegations against Virbhadra Singh has only exposed the double standards of the Congress on corruption issue," he said.He said the people of Himachal Pradesh wanted to know as to what was the reason for the Congress leadership to keep mum over the issue."The developmental has come to a halt in the state as the chief minister is busy in saving his chair," he added.