Who Investigates
The Prime Minister?
Police, Parliament & Constitutional Oversight Explained (2026 Guide)
The Short Answer
No One Is Above Scrutiny.
The Prime Minister can be investigated by several bodies depending on the nature of the allegation. Criminal matters are investigated by the police and prosecuted by the CPS. Ethical or conduct matters are examined under the Ministerial Code, while Parliament provides the ultimate platform for political accountability.
Chapter 01
The Constitutional
Position
As Head of Government, the Prime Minister holds immense executive power, but they do not possess judicial immunity. Their position is defined by accountability to the Crown, Parliament, and the Law.
- • Head of Government
- • Leader of the Executive
- • Member of Parliament
- • Appointed by the Monarch
"The Prime Minister serves at the pleasure of the Monarch but acts only with the confidence of the House of Commons. This structure ensures that no individual holds unchecked power."
Chapter 02
Criminal Investigation
Police Powers
Under PACE 1984, the police have full authority to investigate criminal allegations against the PM. This may involve the Metropolitan Police or external forces to ensure independence.
CPS Standards
The Crown Prosecution Service (CPS) applies the Full Code Test. Prosecution requires both sufficient evidence and a clear public interest mandate.
4. The
Ministerial Code
The Code governs the standards of conduct expected of all ministers. Investigations into potential breaches are carried out by the Independent Adviser on Ministers' Interests.
Focus Areas
- • Conflicts of interest
- • Proper use of resources
- • Integrity and transparency
- • Parliamentary accountability
5. Parliamentary Scrutiny
Parliament holds the PM to account through a variety of mechanisms that ensure transparency and democratic oversight.
Institutional Accountability FAQ
Who investigates the Prime Minister?
Investigations depend on the nature of the allegation: police for crimes, ethics advisers for code breaches, and Parliament for political matters.
Can police investigate the PM?
Yes. The police have full authority under PACE 1984 as the PM holds no personal criminal immunity.
What is the Independent Adviser?
A role responsible for advising the PM on the Ministerial Code and investigating potential breaches upon request.
Can the PM be removed by investigation?
Legal/ethical investigations are part of the process, but removal is typically a political act involving Parliament or the governing party.
What is Judicial Review?
A legal process where the courts examine the lawfulness of decisions made by the government or public bodies.
Can the PM be arrested?
Yes. Legally, the Prime Minister is subject to the same arrest powers as any other citizen (excluding the Sovereign).
DoesParliament have investigative powers?
Select Committees can summon witnesses and request documents to scrutinise government actions.
What happens if a PM is charged?
They would face the standard judicial process. There is no automatic removal from office via charge; it remains a political decision.
Who enforces the Ministerial Code?
Ultimately, the Prime Minister is the arbiter of the code, though the Independent Adviser provides impartial findings.
Can the King remove the PM?
Theoretically, the Monarch can dismiss the PM, but constitutional convention dictates this only happens if the PM loses the confidence of the House.
Institutional
Explainers
Documenting the structures of UK constitutional accountability with absolute neutrality and technical precision.