Tata Institute of Social Sciences: If it's social sciences, it's TISS. With campuses across India in Mumbai, Guwahati, Tuljapur and Hyderabad, you can not only pick your favourite city but also your favourite subject.
University of Delhi: DU has everything, so of course it gets a mention in social sciences list too. No doubt the seats are limited and its highly competitive, but I'm sure you can make it!
Jamia Millia Islamia: This university in Delhi has a few specific PhD options like the one for peace and conflict studies.
Panjab University, Chandigarh: Not only is the campus one of the prettiest around India, the depatments are great for a PhD there. You can avail options like PhD in Defense Studies.
Ambedkar University, Delhi: While it is comparatively new, it boasts of a great faculty and departments. Delhi residents get a leg up but if you have studied in Delhi, you don't need to worry!