Companies who send out spam and unsolicited emails should be black-listed, Secretary for Commerce, Industry and Technology John Tsang Chun-wah said on Monday. Mr Tsang was commenting on a survey conducted by the government. It revealed that 50 per cent of e-mails received in Hong Kong were spam or junk mail. The survey found that five per cent of the unsolicited e-mail originated from Hong Kong, 40 per cent from Asia and the rest was mostly from the United States. Mr Tsang said legislation was not the only way to tackle the problem of spam. 'What we may need to do is to provide a basket of measures, in addition to legislation, which could provide some purposes preventing people interested in doing spamming,' he explained. This would include blacklisting companies responsible for the spam, added Mr Tsang. 'We may also need to look at co-operation with the industry, co-operation with other jurisdictions, and from the technology perspective, how to raise the shield and so forth.' In other developments, Mr Tsang said the government this week would issue a practical guide for mainland companies investing in Hong Kong He said this was the first time that Hong Kong had worked with the Ministry of Commerce in China to issue a step-by-step booklet for investors. 'It's always a good practice that we have a transparent guide that people know exactly what each step is so that they could anticipate what they need to do,' he explained.