The group said the evictions were part of a global crisis which saw an average of six million people illegally thrown out of their homes every year.

The mayor of Beijing, Wang Qishan, admitted on Saturday that in some cases the demolition of homes and evictions had been conducted illegally.

Scott Leckie, the executive director of Cohre, said: "Large international events including global conferences and sporting events like the Olympic Games are mostly accompanied by forced evictions.

"Nearly 100,000 families, over 300,000 people, have been evicted so far in Beijing, and thousands more evictions are expected." He said Cohre, a non-governmental organisation accredited to the UN in Geneva, was calling on the International Olympic Committee to try to stop the evictions.

It was asking companies to withhold sponsorship to countries hosting the games if they carried out evictions. Cohre had reports that Roma residents in parts of Athens had been evicted ahead of this summer's games.