In Sunday’s election Ishiba’s Liberal Democratic Party, which has governed almost continuously since 1955, and its partner Komeito fell a projected three seats short of retaining a majority in the upper house.

Voters angry at inflation turned to other parties, notably the “Japanese first” Sanseito, which made strong gains with its “anti-globalist” drive echoing the agenda of populist parties elsewhere.

“I even think the LDP should have lost more,” 25-year-old Kazuyo Nanasawa, who voted for a small ultra-conservative party, told AFP, adding that Ishiba should quit.

The debacle came only months after Ishiba’s coalition was forced into a minority government in the more powerful lower house, which was the LDP’s worst result in 15 years.

But asked late Sunday if he intended to remain in office, Ishiba told local media: “That’s right.”

He called the election result “extremely regrettable”.

It was unclear in any case who might step up to replace Ishiba given the LDP’s frequent changes of leader in recent years.