Migration experts say the UK cannot end freedom of movement from the EU on Brexit day because it has no system to work out who is legally in the country.
The Home Office said on 19 August that EU freedom of movement would end immediately in a no-deal Brexit.
But Oxford University’s Migration Observatory said employers will have no way to tell whether EU nationals have arrived after 31 October.
It comes as official figures show EU immigration at its lowest since 2013.
Under the existing system, EU nationals do not have to register their presence in the UK so the Home Office does not have records of when they arrived.