Chief Executive Donald Tsang Yam-kuen has been urged to take measures against climate change and attend a United Nations summit in Copenhagen next month to discuss the issue with international leaders.
Environmental group Greenpeace said Tsang and his government had yet to make it clear whether any key Hong Kong official would attend the international conference.
On Sunday, the group launched a month-long campaign asking people to donate HK$1 to raise money to buy Tsang a return air ticket to Copenhagen. Its members erected a portrait of the chief executive in Causeway Bay where people could toss their coins into his mouth.
The UN conference runs from December 7 to 18. It will end two years of negotiations on a global climate change treaty to replace an older protocol drawn up at the 1997 Kyoto meeting on cutting carbon dioxide emissions.
Countries hope the talks will help broker a deal to step up the fight against global warming.
Greenpeace campaigner Prentice Koo Wai-muk criticised Tsang for failing his responsibilities as leader of a world city.