Stepping up its attack on the government over the Sushma Swaraj-Lalit Modi row, the Congress Tuesday demanded a Supreme Court-monitored probe by a Special Investigation Team (SIT) to unearth the “nexus” involving the “senior leadership” of the government which is “protecting and helping” Modi. The party brought the Finance and Home Ministries in its line of attack saying the decision not to appeal in the passport case could not have been taken without their knowledge.