Law, oversight and ethics

How the law governs our work

We work to ensure that what we do is necessary and proportionate, ethical, and compliant with the law. This is part of the culture and values which are a core part of life at MI5. 

Legislation governs our work, explaining what we can and cannot do, and external bodies provide oversight of our work. This framework was determined by Parliament. 

Role and responsibilities of MI5 in law 

The Security Service Act 1989 sets out our functions and gives some examples of the nature and range of threats we work to disrupt. 

In summary, our functions are: 

  • to protect national security against threats from espionage, terrorism and sabotage, from the activities of agents of foreign powers, and from actions intended to overthrow or undermine parliamentary democracy by political, industrial or violent means  
  • to safeguard the economic wellbeing of the UK against threats posed by the actions or intentions of persons outside the British Isles 
  • to act in support to the activities of police forces and other law enforcement agencies in the prevention and detection of serious crime 

We are an apolitical organisation. The Security Service Act makes the Director General responsible in law for ensuring that we do not act to further the interests of any political party. Our role is to protect democracy, not to influence its course. The government of the day cannot instruct MI5 to perform any action for party political reasons. 

We decide independently who or what to investigate and how to prioritise our resources according to threats. 

Powers to gather intelligence 

The Security Service Act 1989, the Intelligence Services Act 1994, the Regulation of Investigatory Powers Act 2000 and the Investigatory Powers Act 2016 provide the legal framework for our intelligence gathering activities. 

These activities include the use of investigatory powers related to: 

  • covert surveillance 
  • covert human intelligence sources 
  • interception of communications 
  • acquisition and examination of communications data, including the bulk acquisition of communications data 
  • bulk interception of overseas-related communications 
  • equipment interference 
  • entry on or interference with property or wireless telegraphy 
  • the retention and examination of bulk personal datasets 

Covert surveillance which is not intrusive, the use of covert human intelligence sources and the acquisition of communications data must be authorised by designated senior staff within MI5. Our use of all the covert investigatory powers listed above is overseen by the Investigatory Powers Commissioner’s Office (IPCO). See below for more information about IPCO. 

Read more about how we gather intelligence

Oversight of investigatory powers 

To use our most intrusive powers, we require authorisation by the Secretary of State, usually the Home Secretary or the Secretary of State for Northern Ireland, and approval from a senior judge. This is sometimes known as the “double lock”. 

A warrant or other authorisation will only be issued where the action is both necessary and proportionate in the interests of national security, or for one of our other statutory functions. 

The Investigatory Powers Commissioner’s Office (IPCO) is the independent oversight body for MI5’s use of investigatory powers. It is made up of the Investigatory Powers Commissioner and a number of other Judicial Commissioners who are responsible for ensuring our use of investigatory powers is lawful, necessary and proportionate. 

This oversight responsibility is met through a comprehensive ongoing review process, which includes audit, inspection, and investigation. 

Visit the IPCO website

Parliamentary oversight 

The Intelligence and Security Committee (ISC) of Parliament oversees the policies, expenditure, administration and operations of the UK’s intelligence community. 

The ISC publishes an annual report and reports on thematic issues. 

Visit the Intelligence and Security Committee website

 Investigatory Powers Tribunal 

The Investigatory Powers Tribunal is a judicial body which offers a route of redress for anyone who believes the UK’s intelligence community has engaged in conduct against them or violated their human rights. 

The Tribunal operates independently and has a UK-wide jurisdiction. There are no costs associated with making a complaint or a Human Rights Act claim to the Tribunal. 

Visit the Investigatory Powers Tribunal website

Inquests, inquiries, criminal and civil proceedings 

MI5 participates fully in inquests and inquiries where their investigations could relate to our work. There are statutory provisions that enable us to provide relevant information to an inquiry, even where that information is sensitive. MI5 officers may also give evidence in criminal and civil legal proceedings. For more information visit the evidence and disclosure page. 


Ethics is embedded in the work we do and integral to the values we hold as an organisation. Our mission is to keep the country safe. Within the legal framework outlined above, the way we achieve that mission is vital to safeguarding the sort of country we live in and sets the UK apart from authoritarian regimes. Our staff can be faced with complex ethical questions and our ethics counsellor is available to staff to help them consider the ethics of their decision making.