BJP and Samajwadi Party today blocked in the Lok Sabha a bill to provide reservation for Scs and STs in government job promotions, delaying the measure which was seen as quid pro quo for BSP's support to UPA on FDI in retail. Just before the House was adjourned sine die after a month-long Winter session, Speaker Meira Kumar regretted that her efforts to get the proposed legislation passed could not succeed.