TOKYO - Japanese Finance Minister Taro Aso said on Monday (June 4) he will voluntarily give up a year's worth of his ministerial salary to take responsibility for a data-tampering scandal that has undermined public trust in the bureaucracy.

Mr Aso, who is also deputy prime minister, apologised for the falsification and attempted discarding of public documents. But he said he had "no intention of stepping down", and that his leadership was critical to regain trust.

Speaking at a news conference, Mr Aso said that in the light of an internal ministry probe, some 20 ministry officials, including former National Tax Agency chief Nobuhisa Sagawa, will be punished with either a fine, suspension, pay cut, or a warning.

The probe, he said, pinned the blame on Mr Sagawa, who was found to have errantly ordered the tampering of at least 14 documents over a dubious sweetheart land deal in Osaka that ensnared Prime Minister Shinzo Abe and his wife Akie.

Mr Abe told reporters an hour after the news conference that he felt "keenly aware" of his responsibility as the head of government.

"There must not be any falsification of official records," he said. "The government, with Mr Aso taking the lead, will implement all possible measures to ensure that this will not happen again."

Mr Sagawa was at the time the chief of the Finance Ministry's financial bureau. While his precise motives remain unclear, the tampering took place after Mr Abe told Parliament in February last year that he will "resign as prime minister and parliamentarian" if he or his wife were found to have been directly involved in the deal.

The piece of public land had been sold at only one-seventh of its appraised value to Moritomo Gakuen, a right-wing nationalist school operator, to build a school that, at one point, was to be called the Shinzo Abe Memorial Elementary. Mrs Abe was to be named the honorary principal.

The rationale for the hefty discount has to do with costs needed to be incurred to clean up the heavily-polluted land - though it has emerged that estimates of the amount of garbage buried under the sold land had been massively inflated.

Former Moritomo director Yasunori Kagoike, who is facing charges for subsidy fraud, has touted his personal ties with the Abes as a reason for the hefty discount, releasing photographs of Mrs Abe visiting the site. The Abes have since distanced themselves from him.

The records were doctored to erase all references of the Abes, senior parliamentarians, the ruling Liberal Democratic Party (LDP) and the right-wing Nippon Kaigi lobby group, which has many supporters in the LDP.

More than 300 sections were deleted, including one in which Kagoike had quoted Mrs Abe as saying: "This is a good plot of land. Please proceed."

Mr Abe has maintained that he and his wife are innocent.

Still, the scandal has cast a light on sontaku, a workplace culture in which subordinates surmise and act on the wishes of their superiors - even if it means breaking the law.

A guilt-ridden official at the Kinki Local Financial Bureau, which was involved in the sale of the land, killed himself over his involvement in the case, and said in his suicide note that he was "just following orders".

Former Finance Ministry parliamentary secretary Toshitaka Oka, an LDP parliamentarian, told the Asahi Shimbun on Monday: "In a closed organisation, employees tend to just obey the orders of their bosses - even if they are bad ones."

He called for reforms for the ministry to be more transparent, saying that "errant instructions will not be possible in an open organisation".

Meanwhile, Osaka prosecutors have said that they will not pursue charges against 38 Finance Ministry officials - including Mr Sagawa - for criminal breach of trust, whether for the sale of state land at a hefty discount or for the tampering of public documents.

In doing so, they said the falsified records do not fundamentally alter the crux of the deal. Japan's conviction rate stands at more than 99 per cent, and prosecutors tend to bring charges only if they are confident of winning a case.

A citizens' group, which includes University of Tokyo emeritus professor Satoshi Daigo, has sought an inquest over the reluctance to charge anyone over the Moritomo case, the Asahi Shimbun reported on Monday.

The report quoted Prof Daigo as saying that if no charges were filed, "democracy in Japan will fall to a new low".

The group is asking the inquest committee to consider mandatory indictments and to rule that the decision not to press charges was inappropriate.

The left-leaning Mainichi Shimbun also lambasted the move in an editorial on Sunday, saying that it sends the wrong signal to the public. In doing so, it cited a Supreme Court precedent in which "one can be convicted of creating false public documents if they had deleted an essential portion of the documents".

Mr Abe continues to be plagued by public suspicions over his alleged involvement in another cronyism scandal. He is accused of pulling strings so that the Kake Gakuen, which is run by a close friend, can open a veterinary school.

He will be hoping that the punishments meted out by the Finance Ministry will, after 16 months, draw to a close the Moritomo scandal.

Trust and support for Mr Abe's administration remain low, according to various media polls, just three months before an internal LDP leadership election that will determine if he can stay as Japan's prime minister until 2021.