Two men travel in a subway coach without pants to campaign for a better environment in Guangzhou, Guangdong province, on the "no pants day" on Sunday.

A group of 20 young people who wanted to call attention to environmentalism by wearing shorts on the subway, instead of their regular trousers, has caused metro operators in Guangzhou to ban any such action in the future. In response to a group of young people who rode the subway without trousers in three days ago, metro operators said the event "posed threats to riding safety and social order".

Between the Wangshengwei and Sun Yat-sen Memorial Hall stations of Guangzhou's metro line 2, some 20 young people rode without trousers on Sunday, with environmental slogans and words written on banners and on their underwear or shorts.

Liang Shuxin, the organizer of the event, said it was aimed at promoting a low carbon lifestyle and an environmentally friendly Asian Games, which will open in the city in November this year.

Related readings: No pants subway ride in Guangzhou Travellers strip for 'No Pants' day Strip your pants off at NYC subway Ye Zichuan, a press official with Guangzhou Metro Corporation, said this unusual happening angered officials with the company after it was reported the next day.

"We did not notice the event on that day since they slipped off their trousers after they entered the coaches," Ye said.

"Their behavior angered not only us, but many parents who have complained to us," Ye told China Daily yesterday.

The company will take every measure possible to stop such unusual events from happening in the future, Ye said.