The Police Ombudsman is to investigate serious complaints about the conduct of immigration and customs officers in Northern Ireland.
The watchdog will investigate Home Office officials and contractors carrying out frontline immigration, asylum and customs duties.
Investigations will be confined to serious matters including deaths but excluding those which happened when immigrants were being escorted or detained by a third party contractor.
Complaints about police and some civilians employed by the PSNI, officers working for the Belfast International Airport, Larne Harbour and Belfast Harbour and Ministry of Defence police will also be covered.
Ombudsman Dr Michael Maguire said: "The Home Office saw there were gaps in their oversight arrangements which meant that should a serious incident take place in Northern Ireland, it could not have been investigated independently."
The move follows an agreement between Home Secretary Theresa May and the Ombudsman.
People with complaints about officials can make them to the Police Ombudsman's Office or the Home Office.
This is the latest extension to the work of the Police Ombudsman's Office in recent years. The office has also been asked to deal with certain complaints about the conduct of officers in the National Crime Agency (NCA).