Carlos Ghosn's lawyers have asked the Tokyo District Court to dismiss all charges against the former Nissan Motor Co Ltd chairman, saying prosecutors colluded with government officials and Nissan executives to oust him from his post.
Ex-Nissan chief Carlos Ghosn on Thursday urged a Tokyo court to dismiss the case against him, accusing Japanese prosecutors of a "pervasive pattern of illegal misconduct".
The claims, made in two filings to the Tokyo District Court, allege prosecutors colluded with Nissan and effectively subcontracted out their investigation to employees of the automaker who were trying to oust Ghosn.
"The court filings demonstrate that the prosecutors' case, which was politically motivated and poisoned from the start, is fundamentally flawed and contradicted by the evidentiary record," Ghosn 's lawyers said in a statement.
Ghosn is out on bail in Tokyo, awaiting trial on four charges of financial misconduct. He denies any wrongdoing and laid out his defence again on Thursday.
But he and his lawyers argue the entire case against him is "fundamentally flawed".
The filings allege the creation of a "secret task force" at Nissan created to "drum up allegations of wrongdoing by Mr. Ghosn as a pretext to remove him".
They formalise claims Ghosn has made previously -- that the allegations against him stem from resentment within Nissan over his plans to more closely integrate the firm with its alliance partner, French automaker Renault.
Along with Mitsubishi Motors, Nissan and Renault form a leading auto alliance, but relations inside the partnership have been tense at times.
Ghosn's legal team claim the opposition to further integration of the car firms drew in even government officials from the Ministry of Economy, Trade and Industry (METI).
"The prosecution against him resulted from unlawful collusion between the prosecutors, government officials at METI, and executives at Nis san," Ghosn's legal team said in a statement.
"Their goal: to oust Mr. Ghosn in order to prevent him from further integrating Nissan and Renault, which threatened the autonomy of one of Japan's industry flagships."
Ghosn's legal team accuses prosecutors of wide-ranging misconduct, ranging from claims they used Nissan employees to investigate and even seize the former tycoon's property, to accusations of discrimination and denying him a speedy trial.
The prosecutor's office had no immediate comment. Ghosn's lawyers attended a pre-trial session on Thursday and will address the media later in the day.
The allegations are the latest twist in a case that has gripped the business community since Ghosn's shock arrest last November.
The formerly high-powered executive was detained as he landed in Tokyo on a private jet and spent 108 days in detention before winning bail and emerging in a bizarre workman's disguise.
He was rearrested not long afterwards, as prosecutors added to his charge sheet, but won bail for a second time after spending another 21 days in detention.
His release came with strict conditions, including restrictions on seeing his wife and bail of $4.5 million.
Ghosn faces a constellation of accusations, including charges for allegedly under-reporting his compensation by more than $80 million over several years.
He argues that compensation was money Nissan had not yet committed to paying him.
He is also accused of funnelling Nissan funds to a friend as compensation for collateral offered to Ghosn. But he says the funds were legitimate payments made to a Nissan dealer and were approved by other executives at the automaker.
And he is alleged to have transferred millions of dollars of Nissan money to a dealership in Oman, skimming off $5 million for his personal ends.
He argues those funds were also approved payments to a Nissan partner and denies any of the money was used by him or his family.
With Thursday's filings, Ghosn's lawyers argue however that the case as a whole should be dismissed.
"This case should never have been brought," they said in a statement, calling it an "abuse of the official authority of criminal prosecution."
But it remains unclear how sympathetic a court will be to the argument, in a system where prosecutors rarely lose cases.
Japanese prosecutors argue their unusually high conviction rate reflects a policy of only bringing strong cases backed by sufficient evidence.
But Ghosn's case has thrown the spotlight on a legal system that detractors argue uses lengthy pre-trial detentions to try to extract confessions from suspects, which critics dub "hostage justice".