Assistant Director of Environmental Protection Eric Chan based his estimate on the observation that air-conditioning accounts for one-third of electricity charges.

He also said that, in an effort to monitor progress, ``energy wardens'' had been chosen among staff at all government departments.

Speaking on World Environment Day, Secretary for the Environment, Transport and Works Sarah Liao said Sunday it is ``ridiculous'' that Hong Kong is regarded as ``one of the coldest air-conditioned places on the planet'' where office workers need to wear sweaters indoor during summer.

She backed calls from concern groups for temperatures to be kept no lower than 25.5 degrees to conserve energy and reduce air pollution from the city's coal-fired power stations.

``The generation of electricity directly leads to air pollution. The public can can also save money,'' said Liao.

Friends of the Earth said it is on the lookout for offenders and will publicize its list of ``thermal criminals'' during the summer.

The move is similar to one employed by the Shenzhen government, which since last year has issued warnings to public places that set their air-con below 25 degrees. Those who failed to comply with the rule will be publicly named.

Public acceptance and observation of the 25.5 degree practice would result in a ``significant reduction of energy consumption, which can help to lessen the greenhouse effect and the release into the atmosphere of chemical refrigerants,'' said Chan.

He also said the government issued guidelines in October instructing all departments to follow the 25.5 degree guideline.

Friends of the Earth is following up on its ``Don't be Cold, be Cool!'' campaign on air-conditioning by calling on people to do their part by reporting to the environmental group if they felt temperatures at workplaces or public are too low.

Since launching its campaign last week, the group said it has received many reports.

It said Wan Chai district council chairwoman Ada Wong complained she felt as if she was being ``frozen to death'' in the Hong Kong Arts Centre cinema.

It called such a waste of energy a ``thermal crime.''.

chester.yung@singtaonewscorp.com