Public prosecutors have questioned former industry minister Yasutoshi Nishimura on a voluntary basis over the slush funds scandal that is rocking the biggest faction of the ruling Liberal Democratic Party, it was learned Saturday.

Nishimura is the sixth faction executive to have been questioned by the special squad of the Tokyo District Public Prosecutor's Office over the scandal.

The other five are former education minister Ryu Shionoya, former Chief Cabinet Secretary Hirokazu Matsuno, former LDP parliamentary affairs chief Tsuyoshi Takagi, former LDP secretary-general for the Upper House Hiroshige Seko and former LDP policy head Koichi Hagiuda.