I think this particular horse bolted long ago.
What needs to be done to curtail immigration of un-skilled labour is to stop agencies from being allowed to employ and farm out otherwise non eligible staff for massive profit.
Currently, labour agencies are able to pay staff about £7.50 ph, (On Zero Hour Contracts), and farm them out at upwards of £14.00 ph to companies that do not have licenses to employ people without 5 yr residency direct.
This Monopoly on hiring labour allows these agencies to advertise abroad and encourage immigration.
Thousands of people are signed up with these companies and struggle on the low wages simply to get their 5 yr, "Quallies", in order to qualify for SS benefits.