A Japanese court on Wednesday rejected a bid by former Nissan boss Carlos Ghosn to end his detention over alleged financial misconduct, a day after he denied all accusations in a dramatic court appearance.

Ghosn's lawyers had appealed to the court to free the auto tycoon, claiming at a special hearing in a Tokyo court there were no grounds for his detention, which has now lasted more than 50 days.

But the court batted off the request, saying in a terse statement: "The request to cancel the detention filed by Mr. Ghosn's lawyers yesterday... was rejected on January 9."

Ghosn stands accused of under-reporting his income in documents to investors, apparently in response to criticism that he earned too much.

He is also under investigation for allegedly seeking to pass off personal investment losses to Nissan's books and paying a Saudi businessman from company funds to stump up collateral to cover the losses.

Ghosn on Tuesday mounted a systematic denial of all the allegations, concluding that he had been "wrongly accused and unfairly detained based on meritless and unsubstantiated accusations".

The presiding judge explained that Ghosn continued to be detained because he presented a flight risk and there were concerns he could tamper with evidence.

On Friday, Ghosn's latest maximum period of detention will end and he will either be freed on bail or -- more likely -- see his detention extended.

Even his main lawyer Motonari Otsuru has acknowledged the 64-year-old executive has little chance of being released soon, describing it as "very difficult" to win bail before the case goes to trial.

And that, he said, could take at least six months.