Charlotte HughesBritish interest in private detectives is surging in 2026, driven by a wave of crime dramas on BBC and ITV and a sharp increase in the number of individuals and businesses seeking covert investigation services. But many people who decide to hire a private investigator — or who discover they are being investigated by one — have no idea what UK law actually permits. The gap between what private detectives can legally do and what their clients assume they can do is a source of serious legal risk on both sides.
Here is what the law says in 2026.
The UK Private Investigation Industry: Largely Unregulated
Unlike solicitors or financial advisers, private investigators in the UK are not subject to a mandatory licensing regime. The Security Industry Authority (SIA) licenses door supervisors and security staff, but private investigation work — following someone, conducting background checks, gathering evidence — is not currently regulated by any single body.
This means anyone can legally call themselves a private detective in the UK. The absence of regulation makes selecting an investigator critically important: a poorly trained or legally ignorant PI can expose you, as the client, to civil liability for the illegal methods they use on your behalf.
The Association of British Investigators (ABI) and the World Association of Professional Investigators (WAPI) both maintain voluntary codes of conduct, but membership is not mandatory and enforcement is limited. A solicitor specialising in private client or family law can advise on how to instruct an investigator without creating legal exposure for yourself.
What a Private Detective Can Legally Do
Within the law, UK private investigators have a surprisingly broad range of legitimate tools.
Public surveillance is their primary method. An investigator can legally follow a subject in any public place — streets, parks, shopping centres, car parks — and film or photograph them from public vantage points. Photographing private property from a public pavement is also generally lawful. The key is that the surveillance must not amount to harassment under the Protection from Harassment Act 1997: systematic, persistent following of an individual with intent to cause distress can cross a legal line even in public spaces.
Open-source research is fully permitted. Investigators can search public registers, Companies House, electoral rolls, Land Registry, court records, and publicly accessible social media to build a profile of a subject. Data collected from genuinely public sources does not normally trigger data protection obligations in the same way as covert collection.
Background checks are lawful when commissioned for legitimate purposes — employment screening, due diligence on business partners, tenancy verification — provided the subject's data is processed in compliance with the UK General Data Protection Regulation (UK GDPR) and the Data Protection Act 2018.
Vehicle tracking using a GPS device is lawful only if the device is placed on a vehicle by or with the consent of the registered owner. An investigator hired by a vehicle owner can legally track their own vehicle. Placing a tracker on a vehicle without the owner's consent — for example, to monitor a spouse — is illegal under the Computer Misuse Act 1990 and the UK GDPR.
What a Private Detective Cannot Legally Do
The list of prohibited methods is equally important to understand.
Intercepting communications — accessing emails, voicemails, text messages, or phone calls without consent — is a criminal offence under the Investigatory Powers Act 2016. No private investigator in the UK has lawful authority to tap phones or access digital communications. Evidence obtained this way is inadmissible in court and exposes both the investigator and the client to prosecution.
Hacking — accessing a computer system, cloud account, or device without authorisation — is a serious criminal offence under the Computer Misuse Act 1990. It is irrelevant that the subject is your partner or business associate: unauthorised access is illegal regardless of the motive.
Trespass — entering private property, including private car parks, residential gardens, or commercial premises, without permission — is not permitted. Evidence gathered on private property without consent may be excluded from legal proceedings and exposes the investigator to civil and criminal liability.
Impersonating officials — pretending to be a police officer, government inspector, or other authority — is an offence under multiple statutes.
Accessing private records — financial data, phone records, medical records, or DVLA data — without consent or legal authority is prohibited. Some disreputable investigators offer these services; instructing them creates liability for the person who commissioned the investigation.
Your Rights If You Are Being Investigated
If you believe you are under surveillance by a private investigator, you have a number of legal rights.
Under UK GDPR, any organisation — including a private investigation firm — that processes your personal data must provide you with a privacy notice and respond to a Subject Access Request (SAR) within one month. If an investigator has collected information about you unlawfully, you can complain to the Information Commissioner's Office (ICO). For the ICO's guidance on how UK GDPR applies to the collection and use of personal data, see ico.org.uk.
If the surveillance is persistent and causing you alarm or distress, it may constitute harassment under the 1997 Act. A solicitor can apply for an injunction to stop it.
The law on surveillance and harassment has been under active review. For the most recent developments in UK stalking and harassment protection, see our coverage of the UK stalking law review submitted to the Home Office in 2026.
When to Consult a Solicitor
If you are planning to hire a private detective — particularly in family law cases involving suspected infidelity, child custody disputes, or financial disclosure in divorce proceedings — consulting a solicitor first is strongly recommended. Evidence gathered unlawfully, or by an investigator who breached UK GDPR, may be inadmissible and can actively damage your case in court.
An ExpertZoom solicitor can advise on the legal boundaries of a proposed investigation, how to structure an instruction to a PI that keeps you on the right side of the law, and what to do if you believe you are being unlawfully surveilled.
Disclaimer: This article provides general legal information only and does not constitute legal advice. Consult a qualified solicitor for advice specific to your circumstances.
