The Official Secrets Act is the United Kingdom’s law criminalising the unauthorised disclosure of sensitive government information. The version currently in force, the Official Secrets Act 1989, replaced an older blanket prohibition with four targeted offences covering security and intelligence, defence, international relations, and crime-related material. A conviction on indictment carries up to two years in prison. Since 2023, it has operated alongside the National Security Act, which repealed the older espionage statutes and introduced offences carrying penalties as severe as life imprisonment.
What the 1989 Act Protects
The Act organises protected information into four categories, each governed by its own section. The categories are not interchangeable: the damage test and available defences differ depending on which section applies.
Security and Intelligence
Section 1 covers information relating to the work of the security and intelligence services, including MI5, MI6, and GCHQ. For current or former members of those agencies, or anyone formally notified that they fall under this provision, any unauthorised disclosure is an offence regardless of whether it causes harm. For other Crown servants and government contractors, the prosecution must show the disclosure was “damaging,” meaning it harmed or was likely to harm the work of the intelligence services.1Legislation.gov.uk. Official Secrets Act 1989 A desk officer at an unrelated department who leaks intelligence material gets the damage test; a former MI5 officer does not.
Defence
Section 2 protects information relating to defence. A disclosure counts as damaging if it harms the capability of the armed forces, leads to loss of life or injury to service personnel, or endangers UK interests abroad. The section covers everything from troop deployment details to weapons specifications.1Legislation.gov.uk. Official Secrets Act 1989
International Relations
Section 3 applies to information about the UK’s relations with other states and international organisations, and to confidential material received from foreign governments. A disclosure is damaging if it endangers UK interests abroad, seriously obstructs the promotion of those interests, or puts British citizens overseas at risk. Confidential information received from another state carries added protection: the fact that it was shared in confidence can itself be enough to establish likely harm.1Legislation.gov.uk. Official Secrets Act 1989
Crime and Special Investigation Powers
Section 4 protects two types of information. The first is any material whose disclosure would result in a criminal offence being committed, help someone escape custody, or impede the investigation or prosecution of crimes. The second is information obtained through surveillance warrants and other covert investigatory powers. Section 4 does not use the word “damaging”; instead, the prosecution must show the disclosure had one of the specific harmful effects listed in the statute.2Legislation.gov.uk. Official Secrets Act 1989 – Section 4
Who the Act Covers
The 1989 Act draws a clear line between insiders and everyone else, and both groups face criminal liability.
The primary targets are “Crown servants,” a term the Act defines broadly: government ministers, civil servants (including diplomats and the Northern Ireland civil service), members of the armed forces, police officers, and certain other appointed officials. Government contractors who provide goods or services to any of these bodies are treated similarly.3Legislation.gov.uk. Official Secrets Act 1989 – Section 12 The scope catches not just the contractor’s business itself but individual employees working on government projects.
Section 5 extends liability to anyone who receives protected information that originated from an unauthorised disclosure by a Crown servant or contractor. A journalist who obtains a leaked intelligence document commits an offence if they pass it on knowing it is protected and, for material under Sections 1 through 3, knowing the further disclosure would be damaging. The prosecution must also prove the original leak came from a British citizen or occurred within the UK, the Channel Islands, the Isle of Man, or a British colony.1Legislation.gov.uk. Official Secrets Act 1989 The effect is to make the chain of secrecy enforceable well beyond government walls.
What Makes a Disclosure Criminal
Three elements typically need to align before someone is guilty of an offence under the 1989 Act. The information must fall within a protected category. The disclosure must lack lawful authority. And for most categories, the disclosure must be damaging or likely to be damaging.
The damage test is the Act’s main safeguard against prosecuting trivial leaks. For defence information under Section 2, the prosecution must show the disclosure harmed military capability or endangered lives. For international relations material under Section 3, the harm must relate to UK interests or the safety of British citizens abroad. The threshold is not abstract embarrassment or political inconvenience. It has to connect to a concrete risk specified in the relevant section.
The big exception is Section 1 as it applies to intelligence service insiders. Members of MI5, MI6, and GCHQ face a strict liability standard: any unauthorised disclosure of security or intelligence material is criminal, full stop. The damage test does not apply to them. A former intelligence officer who reveals information showing the agency broke the law is committing the same offence as one who sells secrets to a foreign government.1Legislation.gov.uk. Official Secrets Act 1989
Liability also attaches to careless handling. Failing to take reasonable care of official documents, retaining classified files after being asked to return them, or neglecting to report a loss can each trigger criminal exposure. The offence does not require a deliberate leak. Negligence that leads to information ending up in the wrong hands is enough.
Defences and the Public Interest Gap
Section 7 defines what counts as a disclosure made with “lawful authority.” For Crown servants, a disclosure is lawful only if it is made in accordance with their official duty. Government contractors must either follow an official authorisation or act within the scope of their contract without breaching any official restriction. For everyone else, the disclosure must be made to a Crown servant carrying out their functions or under an official authorisation. A person charged with any offence under the Act can argue they genuinely believed they had lawful authority and had no reasonable grounds to think otherwise.1Legislation.gov.uk. Official Secrets Act 1989
What the Act does not provide is a public interest defence. There is no statutory mechanism for a defendant to argue that the disclosure, while unauthorised, exposed wrongdoing, illegality, or a threat to public safety that justified the leak. The absence was confirmed by the courts in 2002, when former MI5 officer David Shayler attempted to argue public interest as a justification for disclosing information about alleged security service misconduct. The court rejected the argument.
The Law Commission examined this gap and, in a 2020 report, recommended that a statutory public interest defence be made available to anyone charged under the 1989 Act, including civilians and journalists. The Commission also proposed creating an independent statutory commissioner to whom public servants could report concerns about wrongdoing.4Law Commission. Protection of Official Data As of 2026, neither recommendation has been enacted. The practical result is that whistleblowers who disclose classified information face the same criminal exposure as anyone else who leaks, regardless of motive.
Penalties Under the 1989 Act
Section 10 sets out the maximum sentences. For offences under Sections 1 through 7:
- On conviction on indictment in the Crown Court: up to two years’ imprisonment, a fine with no statutory cap, or both.
- On summary conviction in the Magistrates’ Court: up to six months’ imprisonment, a fine up to the statutory maximum, or both.
A lighter penalty applies to Section 8, which covers the safeguarding of information (failing to return documents, careless handling). Summary conviction for a Section 8 offence carries a maximum of three months’ imprisonment or a fine up to level 5 on the standard scale.5Legislation.gov.uk. Official Secrets Act 1989 – Section 10
Two years may sound modest for betraying state secrets, and it is. The 1989 Act was designed for unauthorised disclosures by insiders, not full-blown espionage. Traditional spying was prosecuted under the Official Secrets Act 1911, which carried a maximum of 14 years. That sentencing gap reflected a deliberate choice: leaking a document to a newspaper was treated as a different order of wrongdoing from passing secrets to a hostile intelligence service.
What the National Security Act 2023 Changed
The National Security Act 2023 is the most significant overhaul of UK espionage law in over a century. It repealed the Official Secrets Acts of 1911, 1920, and 1939, replacing their outdated espionage provisions with a modernised framework.6Home Office. National Security Act Factsheet The Official Secrets Act 1989, which deals with unauthorised disclosures by insiders rather than espionage, remains separately in force.
The 2023 Act creates a new offence of obtaining or disclosing “protected information,” defined as any information where access is restricted, or would reasonably be expected to be restricted, for the purpose of protecting UK safety or interests. To be guilty, a person’s conduct must be for a purpose they know, or ought to know, is prejudicial to UK safety or interests, and the “foreign power condition” must be met, meaning the conduct was carried out for or on behalf of a foreign power.7Legislation.gov.uk. National Security Act 2023 – Section 1
The penalties are much harsher than anything in the earlier Acts:
- Obtaining or disclosing protected information: maximum of life imprisonment.
- Obtaining or disclosing trade secrets: maximum of 14 years’ imprisonment.
- Assisting a foreign intelligence service: maximum of 14 years’ imprisonment.
The jump from the old 14-year maximum under the 1911 Act to life imprisonment reflects the government’s view that the prior sentencing ceiling did not adequately reflect the harm that modern espionage can cause.8GOV.UK. New Espionage Offences Factsheet For the first time in UK law, stealing trade secrets on behalf of a foreign power is also a standalone criminal offence, reflecting recognition that economic espionage can be as damaging as traditional intelligence gathering.9Legislation.gov.uk. National Security Act 2023
How the Two Acts Work Together
Which law applies depends on what the person did and who they were working for. A civil servant who leaks a classified defence memo to a journalist without authorisation is prosecuted under the Official Secrets Act 1989. A person who steals intelligence material and passes it to a foreign government is prosecuted under the National Security Act 2023. The 1989 Act governs unauthorised disclosure. The 2023 Act governs espionage, sabotage, and foreign interference.
In practice, the distinction matters enormously for sentencing. The maximum penalty for an insider leak under the 1989 Act remains two years.5Legislation.gov.uk. Official Secrets Act 1989 – Section 10 The maximum for espionage under the 2023 Act is life imprisonment.8GOV.UK. New Espionage Offences Factsheet Prosecutors choose which statute to charge under based on the facts, and the foreign power connection is the key dividing line.