The former director of a scandal-hit nationalistic educator has turned against Japanese Prime Minister Shinzo Abe and his allies, dishing dirt in a brewing saga that has hurt the leader's solid approval ratings.

Mr Yasunori Kagoike, 64, of school operator Moritomo Gakuen, has embarked on what appears to be a scorched earth campaign against his erstwhile political connections, who now insist they have nothing to do with him.

"Diet members are saying they don't know me at all," he said this month. "But there are those Diet members who know me quite well."

He is a director of the Osaka branch of the influential right-wing lobby Nippon Kaigi, which counts among its brethren Mr Abe and 16 of his Cabinet ministers including defence chief Tomomi Inada.

The group's vision harks back to pre-war Japan, as it advocates the rebuilding of an active armed forces and the indoctrinating of children through reciting imperial decrees.

Mr Kagoike has previously called Mr Abe a great man for taking on the urgent quest to revise the pacifist Constitution, and he used to idolise the leader so much that he had wanted to name his new school the "Shinzo Abe Memorial Elementary".

This school in Osaka is now at the centre of a political firestorm. Its permit to launch next month has been revoked over fraudulent contracts and public furore over a sweetheart deal in which a plot of public land was sold to Moritomo Gakuen for next to nothing. Opposition lawmakers allege political collusion.

Last Thursday, Mr Kagoike dropped a bombshell in a perfunctory remark to reporters that Mr Abe had donated funds to the school through his wife Akie, who was its "honorary principal" until she dissociated herself last month. Mr Kagoike did not elaborate.

Tokyo issued a quick denial, and Mr Abe told the Diet the next day: "I have never met him in person. I have no personal relationship with him. That I would proffer that large a donation to a person like that is inconceivable."

Mr Abe had, in the early days of the scandal, also denied giving Mr Kagoike permission to use his name in publicity materials to raise funds, or to name the school after him.

Mr Kagoike, who has been called to testify under oath in the Diet this Thursday, subscribes to an ultra-nationalist political creed that is evident in his school curricula.

At the Tsukamoto Kindergarten, operated by Moritomo Gakuen, children as young as three years old are made to recite every morning the militaristic Meiji Imperial Rescript of 1890 that calls on pupils to "offer themselves courageously to the State should emergency arise".

The children were made to chant nationalistic jingos at a 2015 sports meet, in praise of Mr Abe for revising laws to expand the Self-Defence Force's role. They also chanted: "We hope China and South Korea, which treat Japan as a villain, will mend their ways and won't teach lies using history textbooks."

Mr Abe has said such conduct was improper, although complicating matters was his wife's speech at Tsukamoto that same year praising the school's ideologies.

Mr Kagoike's nationalistic streak also extends to spouting derogatory insults against China and South Korea, where Japan's wartime atrocities still rankle.

Two years ago, he accused the Japanese Foreign Ministry of being soft in its diplomacy at the expense of national interests, citing territorial disputes such as those concerning the Senkaku/Diaoyu islands with Beijing and Takeshima/Dokdo islets with Seoul, as well as the Nanjing Massacre, which extreme right-wing revisionists deny ever happened.

He said: "If you only want to talk to foreigners or go abroad, go work for a travel agency."

His kindergarten is now under probe for promoting hate speech, while the Osaka authorities are also mulling over criminal action against fraud in the application of the new elementary school.

Mr Kagoike had actively lobbied Liberal Democratic Party lawmaker Yoshitada Konoike to relax regulations for the building of the school by approaching him at least 15 times. Mr Konoike had said in 2008 that he was moved by Tsukamoto children reciting the 1890 Imperial decree.

The plot of land was later sold for one-seventh of its appraised value, and purported contamination of the land meant further subsidies for clean-up costs reduced the final invoice to nearly zero.

Mr Kagoike, who has resigned over his failure to open the school, has said in defiance: "We're working on behalf of Japan. If I don't open this new elementary school, who will? But in response, I'm being called a bad guy, or too stubborn."