The National Accountability Bureau (NAB) on Thursday decided to file a supplementary reference against the former prime minister Raja Pervez Ashraf in connection with his alleged involvement in infamous rental power projects.

Chairman NAB Qamar Zaman Choudhry has given his approval to file the reference against the former prime minister.

Ashraf had been under investigation for his role in granting rental power projects as a water and power minister in the cabinet of ex-PM Yousuf Raza Gilani.

In March 2012 last year, the Supreme Court of Pakistan had declared all such projects unlawful and ordered investigations against the officials, including Ashraf, involved in the scam.