Ishiba, who took office on Oct. 1, plans to dissolve the lower house on Wednesday for an Oct. 27 election.
During his first parliamentary debate with the opposition, Ishiba said he needed a fresh mandate to restore public trust following his Liberal Democratic Party's (LDP) political funds scandal.
"To restore public trust, I will realize politics for the people, not for the politicians," Ishiba told the 465-member House of Representatives.
The new prime minister faced criticism from Yoshihiko Noda, leader of the main opposition Constitutional Democratic Party of Japan, for his abrupt shift in stance on key policy issues and the timing of the election.
Ishiba softened his position on several controversial topics, including the creation of a NATO-style alliance in Asia and revising a Japan-U.S. accord on troops. He also backed away from earlier proposals to impose higher taxes on investment income and allow married couples to use different surnames.
In response to concerns about rising living costs, Ishiba said, "We will take comprehensive steps by giving cash handouts to low-income families most severely impacted by rising prices and providing subsidies to local governments depending on their needs."
