The race for the leadership of the Democratic Party of Japan turned personal on Friday, with deputy leader Katsuya Okada accusing one of his two rivals of flip-flopping over a possible merger with other opposition parties.

Okada said Goshi Hosono had proposed establishing a new party together with Ishin no To (Japan Innovation Party) and the now-defunct Your Party, just a few days before Prime Minister Shinzo Abe dissolved the Lower House in November. He said Hosono now rules out such a realignment and called on Hosono to explain the change.

"There is a huge gap between what he said just before the dissolution of the chamber (and what he says now). Lawmakers must take responsibility for what they say," Okada, a former foreign minister, told journalists in Tokyo on Friday.