Jewellery merchants, for instance, must provide clear details of their merchandise on sales slips.

For gold and platinum products, the weight, standard of fineness, workmanship charges and unit price must be included.

Sellers of diamond jewellery should provide information on the clarity and colour of natural diamonds on request.

More than 3,400 shops and restaurants have been accredited and issued Quality Tourism Services logos since the scheme was launched in 1999.

Membership requirements will now also be tightened to ensure no member has been involved in the sale of fake goods, infringement of intellectual property rights or misrepresentation of product information. Accredited establishments must renew their status every year.

Speaking at a launch ceremony yesterday, Tourism Board chairwoman Selina Chow Liang Shuk-yee said the new requirements would offer visitors stronger assurances. She said the China National Tourism Administration had pledged to help promote the scheme on the mainland. Financial Secretary Henry Tang Ying-yen described the improved scheme as a significant milestone in Hong Kong's service standards.

Secretary for Economic Services and Labour Stephen Ip Shu-kwan and He Guangwei, chairman of the China National Tourism Administration, yesterday signed the Mainland and Hong Kong Closer Tourism Co-operation Agreement. Mr Ip said that under the agreement, the tourism authorities would step up co-operation on joint tourism promotions to attract more overseas travellers to visit Hong Kong and the mainland.