Japan's 2020 Olympic Games president says $2m (£1.4m) in payments relating to the bid process were "legitimate".
A report in the Guardian said the payments were made to a company linked to the son of disgraced ex-world athletics chief Lamine Diack.
Tsunekazu Takeda, who was head of the bid committee for the Tokyo Games, said it was for consulting work.
The payment is being investigated by French prosecutors, while the Japanese government is also looking into it.
The Tokyo 2020 organising committee has denied any wrongdoing.
Takeda says the payments covered "professional services" including consultancy work on "the planning of the bid" and "tutoring on presentation practice".
He added: "All these services were properly contracted using accepted business practices."
The money was paid to Ian Tan Tong Han, who the Guardian reported worked for a subsidiary of Japanese marketing company Dentsu.
But Dentsu says it only has a "business relationship" with the firm in question - Athletic Management & Services.