The Congress party has promised to pass a constitutional amendment to raise the Supreme Court mandated 50 per cent cap on reservations for Scheduled Castes (SC), Scheduled Tribes (ST) and Other Backward Classes (OBC), as per its poll manifesto released on Friday. The party also promised to conduct a nation-wide Socio-Economic and Caste Census to enumerate the castes and sub-castes and their socio-economic conditions.