Reuters, Kuala Lumpur :Malaysian police questioned on Friday former Malaysian Prime Minister Mahathir Mohamad, who is under investigation after calling on the current prime minister to step down over a financial scandal.Mahathir, Malaysia’s longest-serving leader who remains a highly respected and influential figure, has become the fiercest critic of Prime Minister Najib Razak, who is facing pressure over a graft scandal surrounding state fund 1Malaysia Development Berhad (1MDB).In July, the Wall Street Journal reported that investigators looking into the indebted fund had found that nearly $700 million had been transferred into Najib’s bank account.Read: $700m question looms over Malaysia PM as 1MDB anger growsNajib denies wrongdoing or taking any money for personal gain and the state anti-corruption agency said the money was a political donation from an unidentified Middle East benefactor.But that has not stopped the criticism.Mahathir, 90, made a surprise appearance in late August at an anti-government protest in Kuala Lumpur and called for a “people’s power” movement to topple Najib.National Police Chief Khalid Abu Bakar said soon afterwards that the police would take a statement from Mahathir on his comments and they visited his office on Friday to do so, his aide, Sufi Yusof, said.