You see them every summer morning, in the packed commuter trains and offices of Central Tokyo: men dressed in wool and polyester, sweating in the 90F heat. These are the salarymen, the warriors of the Japanese economy, for whom summer is a season more to be endured than enjoyed.

　　From June to September, a fug of humidity falls across Japan, tormenting office workers dressed in a uniform more appropriate for winter. But a salaryman in a T-shirt would be like a samurai without his sword, and there has been no serious challenge to Japan's business dress code for 150 years.

　　This week the Japanese Government embarks on an ambitious scheme to reinvent the appearance of the Japanese businessman. It is being pioneered by fashion designers, famous department stores and captains of industry, and led by Junichiro Koizumi, the Prime Minister, himself.

　　The idea behind the initiative - christened with the English words "Cool Biz" - is simple and serious. Japan is lamentably behind in reaching its targets for reduction of ozone-depleting gases, despite hosting the 1997 Kyoto Conference at which they were set. The stated goal is to reduce 1990 levels by 6 per cent by the year 2012. But in 2003, emissions were up by 8 per cent on the base year.

　　Much of these come from the air-conditioning units, which thrum in Japanese offices during the hot months. So Mr Koizumi has ordered that from June 1 government offices should set the thermostats on their air conditioners for 28C (82.4F) - a little more than Tokyo's average

　　August temperature and intolerable in a suit and tie. The air conditioning will rarely come on, so the Government has launched Cool Biz to persuade salarymen to take off their ties, unbutton their shirts and cast off their jackets instead.

　　"Japanese men are so hard to change," says Hiroko Koshino, a distinguished fashion designer who has devised a range of cool men's clothes at the Government's request. "It's a very, very challenging task."

　　Except at the most youthful of fashion and dot-com companies, casual Fridays never really caught on in Japan. Tsutomu Hata, a former Prime Minister is notorious for his ill-advised energy-saving office wear, created by simply chopping off the arms of conventional suits at the elbow. The garments looked as if a jealous lover had run amok, and are widely held to have set back the cause of dressing down in Japan.

　　The biggest obstacle is the strict hierarchy still operating in Japanese offices - for most salarymen it is unthinkable to indulge any innovation which has not previously been adopted by the boss.