The latest document found in connection with favoritism allegations against Prime Minister Shinzo Abe suggests an Abe administration heavyweight passed on the premier's specific instruction about a university project that would benefit a close friend before a decision was made.

The document released by the education ministry on Tuesday, which dates from October last year, quotes Deputy Chief Cabinet Secretary Koichi Hagiuda as telling a ministry official Abe wanted a veterinary school to be opened in a specially deregulated economic zone by April 2018.

Kake Educational Institution, which is run by Abe's close friend Kotaro Kake, was selected in January to open the vet school at one of its universities in a special zone in western Japan's Ehime Prefecture.

Hagiuda denied on Tuesday having made the remark and said the ministry has already apologized for the explanation it gave, as it was "not accurate."

The latest discovery follows the emergence of 14 other files in an internal probe by the ministry. It could deepen suspicion that the system of special zones, which have looser regulations on certain activities as part of the Abe administration's growth strategy, was used to benefit the educational operator.

Education minister Hirokazu Matsuno told a press conference on Tuesday that the latest document, found in a shared folder, is a personal memo that a ministry staff member created after hearing the head of the ministry's higher education bureau discuss a conversation he had with Hagiuda on Oct. 21, 2016.

The government's advisory council on the special zones did not make a decision on setting up the new vet school until its meeting in November 2016.

But the October memo already mentioned the name of Kake Educational Institution, strengthening suspicion that the plan to benefit Kake was already fixed at that stage.

"It would be out of the question for me to make specific arrangements or give instructions to favor Kake Educational Institution," he said in a statement.

The memo also contains an apparent request to ministry staff to bring up any problems so they could be resolved at meetings between Kake Educational Institution and the ministry, and includes a remark attributed to an aide of Abe's that "the prime minister's office is saying we'll definitely do it."

The government's top spokesman, Chief Cabinet Secretary Yoshihide Suga, stressed Tuesday that all stages of the selection process for the vet school project were carried out in accordance with the law and without bias.

Speaking at a regular press conference, Suga again dismissed suggestions that a third-party investigation is needed in light of the differences in accounts between the ministry and Cabinet Office.

The Democratic Party and three other opposition parties have agreed to seek continued Diet scrutiny of the allegations, even though parliament is not currently in session.

At a press conference on Monday, Abe reiterated his denial of any influence in the project, saying he has only generally made clear that he wants regulatory reform, including through the special zones, to be carried out with a sense of speed.