Refugees who cross the Channel in small boats from Tuesday could face detention and deportation under a new migration law that Labour and charities have called “unworkable” and “cruel”. In an acknowledgment that the law will prompt a fresh rush of refugees across the Channel, the Home Office is seeking to make the illegal migration bill apply retrospectively from the day it is introduced to parliament, the Guardian has been told. Suella Braverman, the home secretary, will ask for the proposed law to be applied from the moment she stands up in the Commons on Tuesday. The move follows criticism from unions that the legislation could result in an increase…