Nobuhisa Sagawa, Director-General of the Ministry of Finance Financial Bureau, answers a question next to Japan's Prime Minister Shinzo Abe and Finance Minister Taro Aso during a lower house session at the parliament in Tokyo, Japan February 24, 2017. Mandatory credit Kyodo/via REUTERS

TOKYO (Reuters) - Former Japanese tax agency chief Nobuhisa Sagawa, a key figure in a cronyism scandal that has sparked a political crisis for Prime Minister Shinzo Abe, will be summoned to testify in parliament on March 27, a ruling party source told Reuters.

Abe’s support ratings have dropped sharply since the finance ministry said it had altered records relating to a discounted sale of state-owned land to school operator Moritomo Gakuen, which had ties to Abe’s wife, Akie Abe.

Opposition lawmakers have been calling for Sagawa, who headed the division that submitted the documents before he became tax agency chief in July, to testify in parliament. Sagawa resigned this month.

Abe and Finance Minister Taro Aso have both denied wrongdoing.

But opposition parties are calling for Aso to resign, while the affair could dash Abe’s hopes of winning a third three-year term as head of his Liberal Democratic Party in a September party leadership election.

Besides Sagawa’s testimony, opposition lawmakers are demanding Akie Abe and other officials testify at parliament, making it unlikely that Sagawa’s appearance as a sworn witness will draw a clear line under the whole affair.