Japanese Prime Minister Shinzo Abe has been grilled in parliament by opposition lawmakers over a widening school land sale scandal linked to his wife, as approval ratings for his Cabinet plunged to their lowest levels.

Opposition lawmakers renewed demands Monday that Abe's wife and top officials involved in the land sale are summoned to testify in parliament. Abe has denied wrongdoing.

Smoldering for a year, the scandal was rekindled after Finance Ministry officials acknowledged tampering with land deal documents, including deleting references to first lady Akie Abe. The ministry's land sale to a school the Abes supported involves a huge discount.

Four media polls released Monday showed Cabinet approval ratings falling to the 30 percent range, the lowest since Abe took office in 2012.