Renault has admitted that it has “concerns” over expenses incurred by the French carmaker’s former leader Carlos Ghosn, adding to his difficulties as he fights similar charges in Japan.

Ghosn’s pay and expenses have come under scrutiny since his arrest and detention in Tokyo for understating his income as president of Japan’s Nissan. Ghosn had been the driving force behind the alliance between Renault and Nissan.

The 65-year-old Frenchman, who was born in Brazil and is of Lebanese descent, has repeatedly denied allegations that he deliberately under-reported his salary by tens of millions of dollars and used company funds to cover personal investment losses.

While Renault initially said it had not found evidence of wrongdoing, it has since shared information with prosecutors.

In a statement issued on Wednesday after a meeting of its board at its headquarters in the Paris suburb of Boulogne-Billancourt, Renault said an investigation had found “questionable and concealed practices and violations of the group’s ethical principles, particularly concerning relationships with third parties, management of conflicts of interest, and protection of corporate assets”.

Renault confirmed it had informed French judicial authorities about separate potential issues centred on payments to distributors in the Middle East. Reuters this week published a report about payments made to an Omani distributor.

The new admission comes on top of previously disclosed issues, including €50,000 (£43,000) paid to the Palace of Versailles to host Ghosn’s wedding in 2016. Renault also said it reserved the right to bring legal action against Ghosn.

Japan’s Jiji news agency also reported that authorities were considering another charge against Ghosn in relation to $32m in Nissan funds paid to an Omani distributor. Some of the funds were believed to have been used to buy a luxury boat for Ghosn and his family.

Renault said it had also found issues with expenses, which may amount to several million euros, that Ghosn claimed from RNBV, a subsidiary of Renault and Nissan.

Renault’s board invited shareholders to vote for Ghosn to be stripped of €224,000 in bonus pay in light of the ethical concerns. Ghosn will also lose some pension entitlements, but he will keep his €1m base salary for 2018.

It was not immediately possible to reach Ghosn’s spokesman for comment.

However, Ghosn had earlier said he was “getting ready to tell the truth” about the scandal. He intends to speak to the media for the first time since he was freed on bail last month. A post on a newly created Twitter account under Ghosn’s name said: “I’m getting ready to tell the truth about what’s happening. Press conference on Thursday, April 11.”

It is unclear whether Ghosn was behind the account, whose 8,000-plus followers appeared to include his son Anthony. The account, apparently verified by Twitter, also tweeted the same statement in Japanese.

Under his bail conditions, Ghosn is not allowed to access the internet and his offline use of computers is restricted to business hours on weekdays at his lawyer’s office.

His 108-day detention in Tokyo attracted international criticism that some speculated was behind a shock court decision to release him in early March on bail set at 1bn yen (£7m) and with strict conditions.

Aside from restrictions on mobile phone and computer use, Ghosn, who left detention disguised as a workman, must remain in Japan. A security camera was installed at the entrance of his home in Tokyo to monitor his movements.