THIRUVANANTHAPURAM : CPM state secretary Pinarayi Vijayan on Sunday said that Kerala Congress leader K M Mani should step down as Finance Minister as the state government had ordered a “Vigilance investigation” into the bribery charges levelled against him by Kerala Bar Hotels Association working president Biju Ramesh. If the Finance Minister is not willing to resign, Chief Minister Oommen Chandy should expel him from the Cabinet, the CPM state chief said.