Welfare Reform Bill

We know from the Government's own impact assessment that under-occupation is a problem particularly, but not exclusively, in the north of England, and that overcrowding is a problem particularly, but not exclusively, in the south. Local authorities have legal duties to their tenants, and if somebody from Salford is seeking to downsize, local authorities in Doncaster or Hull are not permitted to take them because of residency qualifications. Will my right hon. Friend help me to understand something that the Government have completely failed to explain? How will tenants be able to move from one local authority to another?