The governor of Tokyo has stepped down after receiving nearly $500,000 from a Japanese hospital tycoon ahead of his election.

Facing mounting pressure to quit, Governor Naoki Inose, who helped Tokyo secure the 2020 Olympic Games just a few months ago, formalised his resignation on Thursday.

"I have decided to resign from the post of Tokyo governor," Inose told reporters. "I intended to fulfil my duty of explaining to the city assembly, people of Tokyo and people of the nation, but regrettably I could not clear doubts over me. It's solely because of my lack of virtue."

Inose has admitted to receiving the money from the family behind the massive Tokushukai hospital chain ahead of the election, but claimed it was an interest-free personal loan.

He did not declare the sum in his gubernatorial campaign accounts.

Political pressure

An author-turned-politician, Inose, elected as governor a year ago, was one of the most powerful political figures in Japan.

The financial scandal brought substantial political pressure upon Inose to step aside, particularly in the run-up to the 2020 Games.

A special aide to Shinzo Abe said the Japanese prime minister found it "globally embarrassing that the central and Tokyo governments cannot discuss the Olympics" at the moment, according to a report in the Japan Times.

Inose said his resignation was partially aimed at avoiding a negative impact on preparations for the Games.

The 67-year-old also admitted he had been naive about the cut and thrust of Japan's politics.

"I didn't know how strict professional politicians need to be," he said, adding he was unclear about all the procedures he was expected to follow.

"I was an amateur politician even though I knew well about policies. I myself thought it was extraordinary that I became Tokyo governor," he said.

Prosecutors have investigated the Tokushukai group, which runs dozens of major hospitals throughout the country, over allegations of illegal electioneering practices, including providing money to campaign workers when a family member ran for the lower house of parliament.

Source: Agencies