Cooper: How many crossed UK borders without checks?
Home Secretary Theresa May has admitted she does not know how many people came into the UK without proper checks.
An inquiry has been ordered into claims identity checks on travellers from outside Europe were scaled back in the summer, without ministerial approval.
In a statement to MPs, Mrs May said those responsible would be punished.
Shadow home secretary Yvette Cooper said Theresa May should take responsibility for what had happened.