Singh said that he "welcomed" the government's decision on Article 370 which gave special status to Jammu and Kashmir. He joined the league of several Congress leaders who supported the government even when the Congress party has stood against the move.
According to sources close to him, Singh has cited the party's stand on abrogation of Article 370 as his reason for resignation.
When asked about joining BJP, he said "I have given the resignation as of now. I will take the right decision at the right time."
Earlier, another Congress leader actor-turned-politician Urmila Matondkar resigned from the party citing inaction on the part of "key functionaries of Mumbai Congress" for the "betterment of the organisation".
She had joined the Congress ahead of general elections and unsuccessfully contested from Mumbai North constituency.