In much-anticipated sworn testimony at the Diet, a former Finance Ministry official categorically denied Tuesday any involvement of Prime Minister Shinzo Abe, his wife or his top allies in a document falsification scandal that has rocked the government by pushing down voter approval rates in recent media polls.

"It was never reported to the Prime Minister's Office. It's something that was conducted internally by the Financial Bureau" at the Finance Ministry, claimed Nobuhisa Sagawa, a former National Tax Agency head who oversaw the bureau when the document tampering is reported to have occurred — between February and April last year.

Sagawa gave the testimony as a sworn witness, meaning he would be punished if he lied or refused to speak without legitimate reasons.