How the law governs our work

Our mission is to keep the country safe. Everything MI5 does is within a framework defined by the law, which clearly sets out that all our actions must be necessary and proportionate. Operating ethically is at the heart of the culture and values of MI5. 

The law applies to all our work, providing the legal framework within which we operate and governing what we can and cannot do. This framework was determined by Parliament and includes not only the laws that set our functions and powers, but also the Human Rights Act. We can interfere with human rights only where strictly necessary and proportionate to meet our statutory functions under law. 

Our powers and how we use them are overseen by independent external bodies, judges and ministers. The Director General of MI5 is accountable to the Home Secretary.

DG Sir Ken McCallum says:

“Law and ethics are at the heart of everything that MI5 does. The law governs and enables our critical work in keeping the country safe. Within MI5, we have a strong culture of ethics – everything we do is guided by the principle of doing only what is necessary and proportionate. Our people make tough decisions every day, ensuring that they are in line with the law and with those strong ethical principles. The nature of our work means that these considerations have to be, and are, always at the forefront of our minds.

When, in the course of their work, our staff have ethical questions or concerns, we have systems in place (including access to our ethics counsellor) for them to raise and discuss such issues.”

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 

As a public body we are bound by the Human Rights Act. This means that in our work we can only use our powers in a way that interferes with human rights when it is necessary and proportionate to do so. In addition to those legal provisions, ethics are a core part of MI5’s culture and sit closely alongside our adherence to the law in guiding our approach and use of our powers (see ethics below). 

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 are operationally independent. This means that we determine what threats to investigate and how to prioritise our resources. The Director General has control of, and is responsible for, MI5’s operations.

Powers to gather intelligence

Our intelligence gathering powers are set out in the Security Service Act 1989, the Intelligence Services Act 1994, the Regulation of Investigatory Powers Act 2000 and the Investigatory Powers Act 2016 (amended in 2024). This framework is designed to ensure that we comply with the Human Rights Act.

Our investigators powers relate 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 a 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 one of our other statutory functions). 

The Investigatory Powers Commissioner’s Office (IPCO) is the independent oversight body for MI5’s (and other organisations’) 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 and continuous process of review, which includes audit, inspection, and investigation. 

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 fully participates in inquests and inquiries where our work could relate to their investigations. There are statutory provisions that enable us to provide relevant information to an inquiry, even when 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 

Ethics is embedded in the work we do and is central 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 go about achieving that mission is important. That means safeguarding our country in a way the population we serve would expect us to and in a way that sets the UK apart from authoritarian regimes.

Our staff can be faced with complex ethical questions and for that reason we have an ethics counsellor who is available to our staff to help them consider ethics in their decision making.