Education minister Yoshimasa Hayashi said Tuesday he has given final approval for a new veterinary school at the center of cronyism allegations leveled at Prime Minister Shinzo Abe, drawing rebukes from opposition parties.

The school operator, run by Abe's close friend Kotaro Kake, is now set to launch in April the country's first new veterinary department in over half a century, in a government-designated deregulation zone in western Japan, despite the scandal that at one point hurt the prime minister's approval ratings.

Suspicions remain as to whether Abe used his influence to sway a government decision to set up the school, as suggested by leaked documents from the education ministry.

Opposition parties which had demanded Hayashi put his decision on the school on hold are set to intensify their offensive against the premier. Abe has flatly denied any involvement.

Hayashi told a press conference the project has been judged to comply with laws and rules, including standards to set up universities.

"I have decided to approve the project in light of (an education ministry panel's) report," he said. Last week, the panel gave a green light to the school opening.

Hayashi also said he has confirmed the project is "in line with the school operator's plan that has been approved in the (monitoring) process under national strategic economic zones," adding, "there were no defects" in the process.

Opposition parties have raised questions over the vet school project as they doubt it meets four conditions set by Abe's Cabinet in June 2015, including that a new institution is supposed to deal with problems which are hard for existing universities to address.

Chief Cabinet Secretary Yoshihide Suga echoed Hayashi's view, telling a separate press conference that opposition claims on the matter were unfounded.

But Akira Nagatsuma, a senior lawmaker of the leading opposition Constitutional Democratic Party of Japan, called the approval "outrageous" and urged the government to withdraw it and provide a thorough explanation on the issue.

Seiji Mataichi, secretary general of the smaller opposition Social Democratic Party, said Abe "benefited his buddy by using politics for his private purposes" and called for Diet deliberations on the matter.

Kotaro Kake said in a statement that the operator Kake Educational Institution "will make efforts to enrich (the new school's) education and research program to train human resources who can play active roles in the world."

In approving the project, the panel listed eight points of concern. For example, it called for the operator to ensure the proposed quota of 140 students, one of the largest in Japan, does not inhibit the quality of educational research.

In January, the Abe government approved Kake's plan to construct the new department in the deregulation zone in Imabari, Ehime Prefecture. In March, the school operator sought approval for the project from the Ministry of Education, Culture, Sport, Science and Technology.

The ministry panel overseeing new university projects had planned to reach a conclusion on the issue in August but put the decision on hold after the favoritism allegations surfaced, citing problems in the school's education program.

The government had not given consent to the opening of a new veterinary school for five decades amid concerns about a glut of veterinarians.

Despite Abe's repeated denial of his involvement in the approval process, documents found at the education ministry have indicated that officials at the Cabinet Office, which oversees specially deregulated economic zones, pressured the ministry ahead of the government decision to allow Kake to construct the school building.

The papers contained phrases such as "what the highest level of the prime minister's office has said" and "in line with the prime minister's wishes."