Many are detained - often for many months - over debts incurred by their employers. Authorities say they will not be released until the money is paid.

SAR officials have been accused of not doing enough to help such detainees and have been pressing mainland counterparts for action.

The SAR asked for such a mechanism last summer, but no agreement has been reached.

Director of the SAR's Beijing office Bowen Leung Po-wing said yesterday the issue was complicated as it involved various mainland departments.

Either the Public Security Bureau (PSB), Customs, Supreme People's Procuratorate or courts could detain people.

A dozen laws had to be changed before a notification system for all departments could be implemented, Mr Leung told a special Legco Finance Committee meeting.

But as most cases related to the Public Security Bureau, the bureau had drafted its own notification system.

'An internal study is at the final stage because it involves some legal questions,' he said.

There was no indication as to when the system might start.

Once it was set up, the mainland's Hong Kong and Macau Affairs Office, which plans the notification system as a whole, could start work.

Democrat Cheung Man-kwong said SAR detainees' families wanted to visit their relatives.

'But the Beijing office is not allowed to represent the families visiting the detainees since Hong Kong people cannot enjoy any consular protection since Hong Kong returned to China,' Mr Cheung said.

Mr Leung said the SAR Government had made the request when discussing the notification system, but there had been no reply.