The isolation bubble system that Olympic organisers have set up at the Tokyo Games village to control Covid-19 is already broken, and there is a risk that infections could spread more widely from inside it, a prominent public health expert has said.

International Olympic Committee President Thomas Bach had said last week that testing and quarantine protocols would leave “zero” risk of Games participants infecting residents in Japan.

Kenji Shibuya, the former director of the Institute for Population Health at King's College London, said such declarations only served to confuse and anger people as actual conditions on the ground were “totally opposite”.

“It's obvious that the bubble system is kind of broken. My biggest concern is, of course, there will be a cluster of infections in the village or some of the accommodation and interaction with local people.” Reuters quoted him as saying.