TOKYO (Reuters) - Japan’s Prime Minister Shinzo Abe, his wife, Finance Minister Taro Aso and their top aides did not give instructions to change documents about a land deal at the heart of a suspected cronyism scandal, a former finance ministry official said on Tuesday.

Slideshow ( 9 images )

But the sworn testimony in parliament by Nobuhisa Sagawa, formerly head of the finance ministry division in charge of the documents, failed to erase doubts of opposition lawmakers, who again called for Abe’s wife, Akie, to answer their questions.

Sagawa declined to comment on motives for altering the documents because he is a subject of investigations into the matter.

The suspected scandal and possible cover-up have slashed Abe’s ratings and clouded his chances of a third three-year term as ruling Liberal Democratic Party (LDP) leader in a September party vote.

The finance ministry admitted on March 12 that it had altered documents about a heavily discounted sale of state-owned land to school operator Moritomo Gakuen, which had ties to Abe’s wife, Akie.

“This is a matter concerning the process of altering the documents. Who ordered it and how the alteration was carried out are the targets of investigation,” Sagawa said.

“I would like to refrain from answering because there is a risk of criminal prosecution,” he said.

But Sagawa, who resigned as National Tax Agency chief this month, said that he did not think that Abe or his wife influenced the land sale itself.

Abe has repeatedly denied that he or his wife intervened in the sale or that he ordered a cover-up but public doubts have persisted. Opposition lawmakers want his wife to answer questions in parliament but the premier is against that.

“The doubts have deepened,” opposition Constitutional Democratic Party of Japan senior lawmaker Tetsuro Fukuyama told Sagawa. “You have poured oil on the fire.”

A Nikkei business survey published on Monday showed support for Abe, who took office in December 2012, had sunk to 42 percent while those opposed to his cabinet jumped to 49 percent.

A separate survey by Asahi News Network (ANN) showed his approval rating fell to 32.6 percent while those disapproving accounted for 54.9 percent. Forty-eight percent of respondents to the ANN survey said Abe and his cabinet should resign, against 39 percent who said there was no need to do so.