However, council vice chairman Ron Hui Shu- yuen says the contaminants are unlikely to have any effect unless a person drinks in excess of 50 cups of tea daily.

Tests by the council focused on 46 samples - 32 leaves and 14 bags - sourced from supermarkets, teahouses and restaurants.

Although only one sample contained excessive lead and another excessive pesticides, all samples had traces of such contents.

A sample of oolong tea leaf sold by Choi Wan Hin Seafood Restaurant in Tsim Sha Tsui contained 9.3 milligrams per 1000 grams of lead, exceeding the safety limit of five milligrams per 1,000g stipulated in the Chinese national standard.

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The China-origin Shen Long Chinese Tikuanyin tea bags contained 0.342 milligrams per 1,000g of DDT residue, which exceeds the safety limit of 0.2 milligram per 1,000g.

Three samples of tea containing the most lead were brewed for 30 minutes and the results showed the maximum level of lead detected was 19 micrograms per liter. The lead content comes from the soil, water or tools for food processing while pesticides can be found in soil, according to the council's Choice magazine.

Hui said contaminated tea leaves were unavoidable and suggested consumers make wise choices when buying.

Hui said the density of lead and DDT residue contained in the samples is unlikely to exceed the safety standard unless a person drank more than 13 liters, or the equivalent of 52 cups, of tea.

"One usually drinks eight glasses of drinks a day, totaling two liters, so unless he or she takes in lead or DDT from other sources, the normal consumption of tea is unlikely to reach the daily threshold," he said.

Hui advised consumers not to soak the tea leaves for too long, and to rinse them before brewing. He also advised against swallowing the leaves.

The distributor of Shen Long refused to accept the council's report, saying it varied from the company's test results.

The Centre for Food Safety has retested samples found to contain lead and pesticide and the results have been satisfactory.