National Accountability Bureau (NAB) on Monday filed a supplementary reference against former prime minister Nawaz Sharif and his family over their four upscale Avenfield flats in London, sources told DawnNews.

The reference features fresh evidence, including TV interviews given by Sharif, his daughter Maryam Nawaz, and his two sons Hassan Nawaz and Hussain Nawaz.

The reference also features seven new witnesses, including Britain-based forensic expert Robert Radley and a close relative of Wajid Zia — who headed the joint investigation team that probed the Panama Papers case. The duo's statements have already been recorded.

Also listed as witnesses are two officials from the Ministry of Information, two from NAB and one from a private TV channel.

The Avenfield Properties reference alleges that Sharif, his brood and his son-in-law, retired Captain Mohammad Safdar, had purchased four flats in Park Lane, UK, without legitimate financial means.