The Finance Ministry admitted Monday to having altered documents over a discounted state land sale at the center of cronyism allegations against Prime Minister Shinzo Abe, with references to him and his wife, whose role in a school project is suspected to have led to the reduced price, being deleted.

The document falsification "could erode public trust in the entire government and I feel responsible as someone at the top of the government," Abe told reporters in his office. Abe has denied his or his wife's involvement in the controversial land sale deal.

The admission in a report to the Diet raised pressure on Finance Minister Taro Aso to step down to take responsibility for the alterations. But Aso told reporters he has "no intention" to resign, while offering a "deep apology" over the matter.

Abe indicated he sees no need for his key ally, who also serves as deputy prime minister, to resign, by saying he hopes Aso would lead efforts to "look into why such a thing happened" to regain public confidence.

The scandal involving school operator Moritomo Gakuen has haunted Abe for more than a year since it was first reported in February last year and could dent his hopes of winning the Liberal Democratic Party's presidential race in the autumn and becoming Japan's longest-serving prime minister.

Opposition parties ramped up pressure to topple the Abe administration, reaffirming their cooperation to summon Akie Abe to the Diet as a sworn witness, a demand the ruling bloc once again rejected Monday. The opposition camps claim the ministry drastically reduced the price of the land because of Akie Abe's role in the project.

The original documents quoted Moritomo, which was planning to build an elementary school on the site in Osaka, as saying the prime minister's wife had recommended the project "move forward because it is a good plot of land." The documents also said she inspected the operator and gave a speech there in April 2014. But they were erased in the documents later disclosed to lawmakers.

Akie Abe was initially named honorary principal of the school but withdrew after the controversial state land deal came to light in February 2017.

Regarding the land sale reached in June 2016, Abe told parliament in February last year that he "would quit as prime minister and as a Diet member" if evidence was found proving their involvement. But the point remains unclear, even after the release of the ministry report.

Aso said the documents were changed at the instruction of some officials in the ministry's Financial Bureau in charge of overseeing the land sale, in an apparent bid to make them consistent with what Nobuhisa Sagawa, who formerly headed the section, told parliament.

Amid the unfolding controversy over the dubious state asset transaction, Sagawa stepped down as National Tax Agency head on Friday. He had been under pressure for allegedly making false remarks to parliament over the land sale.

Criticism surfaced even within the ruling bloc. Toshihiro Nikai, the LDP's secretary general, said in a press conference the document falsification was "unimaginable" and a "serious problem that cannot be explained simply as an 'error.'" Natsuo Yamaguchi, who heads the LDP's junior coalition partner Komeito party, told reporters in the Diet the deed "can by no means be tolerated."

References to Abe and Aso in the original documents as senior members of a parliamentary group supporting the conservative lobby organization Nippon Kaigi, or Japan Conference, were also deleted. The papers had said Yasunori Kagoike, who headed the school operator at the time of the controversial land sale, had ties to the body's Osaka branch.

The scandal, which has pushed down Abe's support ratings, has drawn fresh attention since The Asahi Shimbun daily's March 2 report on the doctored documents.

Political analyst Atsuo Ito said the chances of a resignation en masse by the Abe Cabinet are low since the ruling parties account for a majority in both chambers of the Diet. But if the premier "fails to provide a convincing explanation to the public, his support rate would further drop and force him to give up running for the LDP presidential race in September," Ito said.

The ministry said 14 of the original documents were rewritten between February and April last year after the scandal emerged. Descriptions saying the dramatically cut land sale price was "exceptional" were omitted in the versions later disclosed to Diet members. The names of several politicians, including former trade minister Takeo Hiranuma and former disaster management minister Yoshitada Konoike, were also erased.

The state-owned land in question is an 8,770-square-meter plot in Toyonaka, Osaka Prefecture, that was sold to Moritomo for about 134 million yen ($1.25 million) to build a new elementary school, far below its appraised value of 956 million yen.

Prosecutors are investigating Finance Ministry officials on suspicion of selling the plot at an unreasonably cheap price and discarding negotiation records that should have been kept.

The ministry has claimed the heavily discounted sale price was calculated in light of the costs to dispose of buried waste at the site. But the Board of Audit of Japan warned in November the discount happened because the price was not properly calculated.

Kagoike and his wife Junko have been indicted on unrelated subsidy fraud charges.