The board of Nissan has voted to sack its chairman, Carlos Ghosn, days after his arrest for alleged financial misconduct sent shockwaves through the business world.

The seven-member board voted unanimously to dismiss Ghosn, who is credited with saving the carmaker from bankruptcy when he took over almost two decades ago and forging a successful alliance with Renault and Mitsubishi Motors.

Renault appointees on the Nissan board supported the decision, which may begin to defuse a crisis that threatened to upend the alliance and spark a diplomatic rift between Japan and France, Renault’s main shareholder.

Nissan said in a statement that the board “acknowledged the significance of the matter and confirmed that the long-standing alliance partnership with Renault remains unchanged, and that the mission is to minimise the potential impact and confusion on the day-to-day cooperation among the alliance partners”.

The firm said it would create a special committee – led by its three independent directors, including the racing driver Keiko Ihara – that will take advice from third-party experts on how to improve its management system and governance of directors’ pay. It will also set up a committee to oversee the appointment of Ghosn’s successor as chairman.

Thursday’s decision, part of the company’s attempts to navigate the biggest scandal in its history, came days after Hiroto Saikawa, Nissan’s chief executive and once a close Ghosn ally, launched an extraordinary attack against his former mentor after his arrest at a Tokyo airport on Monday.

Saikawa said Ghosn had enjoyed “too much authority” during his time at the helm of Nissan, and referred to “the dark side of the Ghosn era” as he called on fellow board members to sack him.

Sources close to the company said Saikawa, who is among those in line to replace the 64-year-old Ghosn, went into Thursday’s board meeting confident that other Nissan executives would back his demand for his dismissal.

“This would not have been proposed if there had been any doubt and the results of the investigations have already been presented to the board members,” the source told Agence France-Presse.

Ghosn, who is being held at a Tokyo detention centre, has not been seen in public or made any comments since his arrest.

In contrast to the lavish lifestyle to which Ghosn was accustomed, inmates at the centre are permitted just 30 minutes of daily exercise and two baths a week.

One lawyer familiar with the facility said the austere single rooms for each prisoner have only a bed, a toilet and a handle-less door with an iron-barred window. Detainees are woken shortly before 7am and lights are out at 9pm.

On Wednesday, local media reported that prosecutors had successfully applied to extend Ghosn’s custody by 10 days. Under Japanese law, suspects can be held for 20 days per possible charge without an official indictment. Additional charges can be added, resulting in longer detentions.

Shin Kukimoto, a deputy public prosecutor, refused to comment on Thursday on whether Ghosn, who has yet to be charged, had admitted to the allegations.

Prosecutors believe Ghosn and an American executive, Greg Kelly, “conspired to understate Ghosn’s income five times between June 2011 to June 2015”, reporting a total of 5bn yen in income ($44m) instead of the actual 10bn yen.

The Nissan board also voted to remove Kelly from his position as representative director, with the company describing him as the “the mastermind of this matter, together with Carlos Ghosn”.

Nissan said on Monday that an internal investigation launched after a tipoff by a whistleblower had also revealed that Ghosn allegedly misused company money.

The public broadcaster NHK said Nissan had paid “huge sums” to provide Ghosn with luxury homes in Rio de Janeiro, Beirut, Paris and Amsterdam “without any legitimate business reason”.

The Yomiuri Shimbun newspaper, quoting unnamed sources, said Nissan’s investigation had uncovered evidence that, starting in 2002, Ghosn instructed that about $100,000 a year be paid to his elder sister as remuneration for a non-existent “advisory role”.

The Asahi Shimbun newspaper quoted unnamed sources as saying that Ghosn gave Kelly orders by email to make false statements on his remuneration. Prosecutors are believed to have seized the emails, according to a report in the Japan Times.

Ghosn’s arrest has prompted questions about whether the alliance of Nissan, Renault and Mitsubishi Motors, which employs 450,000 people around the world, can survive without Ghosn.

This week Renault voted to keep him as its chief executive but appointed Thierry Bolloré, the chief operating officer, as interim chief.

According to the Financial Times, Ghosn’s fall from grace came as he was working on a full-blown merger between Nissan and Renault, at the French government’s urging, despite strong reservations among Nissan executives.

“For me, the future of the alliance is the bigger deal,” a senior Nissan official told reporters on Wednesday, when asked about Ghosn’s arrest. “It’s obvious that in this age we need to do things together. To part would be impossible.”

Mitsubishi plans to remove Ghosn from his post of chairman at a board meeting next week.

Despite Nissan’s decision to sack the pair, Ghosn and Kelly will stay on as board members and can only be removed by shareholders.