Shinzo Abe might be forced to resign if his ruling party suffers a heavy defeat in next month's upper house elections, according to one of the Japanese prime minister's potential successors.

Sadakazu Tanigaki, finance minister in the previous administration, said in an interview with the FT last night: "The resignation of Abe is not out of the question, though we are doing our best to prevent it. But if we lost badly, it would be hard to pass legislation and so nothing would move forward." He added: "Historically, when the Liberal Democratic party has lost a lot of seats, somebody has been held accountable."