THE policy against importing domestic helpers from China was unlikely to change because this could send the wrong signal to illegal immigrants and overstayers, said the Secretary for Security, Alistair Asprey. ''There would be difficulties with maintaining effective immigration control if domestic helpers from China were permitted to enter,'' he said. It would be difficult to prevent abuses, such as people seeking to bring in family members from China by representing them as domestic helpers. Mr Asprey said they could become permanent additions to the population if they fulfilled the seven-year residency requirement. It would be difficult to detect overstayers, and would-be illegal immigrants might get the wrong signal.