Four best-selling cigarette brands contain significantly more tar than their labelling claims, but the Government has so far refused to name the offenders. The manufacturers, identified in tests by government chemists, face no action because the law allows them 12 months to change their advertised tar grouping. But anti-smoking activists fear improper labelling could mislead smokers and endanger their health. They are now demanding tougher laws. The Government yesterday published the tar and nicotine yields of Hong Kong's 91 best-selling brands last year, without naming any. Two cigarette brands were tested in the high tar group (18 to 20 milligrams per cigarette), 40 in the middle tar group (15 to 17 mg), 27 in the low to middle tar group (10 to 14 mg) and 22 in the low tar group (0 to 9 mg). Government chemists found four brands labelled 'low to middle tar' had tar levels which should have placed them in the 'middle' tar group while another two brands were labelled as being in a higher tar group than tests showed. The Health and Welfare Bureau refused to reveal brand names. Council on Smoking and Health chief Marcus Yu Yin-sum urged the Government to introduce the amended smoking ordinance soon. The amended law, passed last year, still has to have a date set by the Government for its official enactment. 'We hope the Government can speed up the pace,' Mr Yu said. 'The sooner the law is in place the better people will be protected, although under the new law a similar inconsistency between claimed and real tar content might still exist.' A bureau spokesman said the new law would allow manufacturers six months instead of the current 12 to change their labels. Cigarette packets would also have to carry their exact tar and nicotine yield instead of the current system of tar grouping.