Friends of the Earth said workers should dress casually for the office in summer to help cut down the need for air-conditioning.

FOE also said the government and chief executive candidate Donald Tsang should take the lead and set the pace in sartorial environmentalism to keep indoor temperatures no lower than 25 degrees Celsius.

The group's statement comes after a survey of 17 office premises conducted by the Hong Kong Polytechnic University, which found indoor temperatures of most offices hovering around 21C and 22C, with the coolest a winter-like 17.6C.

It is common practice in Hong Kong to keep indoor temperatures low, with staff often having to wear jackets in summer.

FOE director Mei Ng said air-conditioning accounts for 60 percent of the city's electricity consumption in summer. She pointed out that every one-degree Celsius rise in indoor temperature equates to a 3 percent saving in electricity consumption.

``If everyone in Hong Kong does that [maintains offices and homes at 25 degrees Celsius], this alone will save about 330 million units of electricity and cut emissions of carbon dioxide by 2.5 million tonnes a year,'' Ng said.

``Just to capture that amount of carbon dioxide in a year would need a forest eight times the size of Hong Kong.''

She urged people to make more use of electric fans, which consume much less power, in order to keep indoor temperatures at comfortable levels.

She said suits and ties are totally unsuitable for Hong Kong's hot and humid sub-tropical weather.

Office workers should dress casually, with unbuttoned collars and roll-up shirtsleeves, instead of turning up the aircons.

She said chief executive candidate Donald Tsang should shoulder more responsibility for environmental protection.

teddy.ng@singtaonewscorp.com