The environmental group is "deeply concerned" that the Committee followed "protocols that fell far below globally accepted sustainability standards", especially for timber, fishery products, paper and palm oil to be used for the Games, according to The Mainichi newspaper.

WWF has sent a letter to the International Olympic Committee (IOC), requesting disclosure of procurement results, including origins and ratios of certified products, and an external valuation.

"As the host country of the Tokyo Olympics, Japan is responsible for sourcing and consuming products in a sustainable way," WWF-Japan chief executive Ron Tsutsui said.

"If the Tokyo Olympics fails to lead sustainable sourcing, how can it lead future Olympics or leave a legacy for Japanese society to transform to be more sustainable?"

The group also want an end-of-year report based on the external valuation, claiming that the Organising Committee had "showed little regard" to advice from experts to to develop world-class sourcing protocols.

However, the Olympics Organising Committee has refuted the claims, claiming that the developed procurement codes recognise feasibility and used standards created by global organisations such as the Forest Stewardship Council and Marine Stewardship Council.

But the Committee has also said it will study the WWF request for a report and external review.