"Any event should be conducted in accordance with regulations and should be accepted under social ethics. Riding without trousers in public areas such as subways is not acceptable by the majority of people," Ye said.

Sources with the company said anyone riding in the subway without pants would be punished in accordance with civil regulations.

The event on Sunday was one of the many that has already taken place in some 44 cities across 16 countries and regions. It was believed to be the first of its kind across Chinese cities.

"It will bring about negative impacts to some people, specially senior citizens and parents. They hardly know relations between no-pants riding and environmental protection," said Cao Yixin, a student with Sun Yat-sen University.

Participants should take Chinese culture into consideration when they take part in such events, Cao said.

"Many Chinese people, even us college students, can hardly accept such a move in public areas," she told China Daily.

Huang Huiju, a mother with a 7-year-old daughter, said the move had nothing to do with environmental protection.

"I don't see any relation between such a move and a lower-carbon lifestyle. Trousers are necessities we need every day," she said.

Huang and her daughter were among hundreds of passengers to witness the campaign on Sunday.

"I covered up my daughter's eyes. A young man quickly took off his trousers after he entered the coach. It made me very embarrassed," she said.