The independent Kunda legislator was asked by the Central Bureau of Investigation late Tuesday night to be present at the CBI camp office at 10.30 am Wednesday, CBI sources said.
The development comes amid reports that the agency has found no "direct wrong doing" on part of the former minister. Parveen Azad, the widow of the slain police official had accused Raja Bhaiyya of involvement in the murder.
Following the allegations and his name surfacing in the first information report (FIR), Raja Bhaiyya was asked to resign from the cabinet by Chief Minster Akhilesh Yadav.
Raja Bhaiyya held the food and civil supplies portfolio in the Akhilesh Yadav government. Several close aides of the former minister, including his legislator cousin Akshay Pratap Singh has already been questioned by the CBI team investigating Haq's murder.
Haq was killed March 2 in Kunda in Pratapgarh after an angry mob ran berserk following the murder of Balipur village head Nanhe Yadav and his brother Suresh Yadav.
The mob chased and beat up Haq even as his security guard and other policemen left him alone to face the fury of the crowd. Four cases have been registered by the CBI for the triple murders. The CBI is expected to file a report on the probe by May end.