Owning a Car Key Signal Jammer Now Means Five Years in Prison

Owning the small handheld gadget used to steal modern cars from driveways across Britain is now a serious criminal offence carrying up to five years in prison and an unlimited fine, after the Crime and Policing Act 2026 received Royal Assent and the Home Office published its serious crime factsheet on 11 May. For the first time, police can seize signal jammers and relay devices on the spot without having to prove the holder was about to use them in a specific theft. For honest drivers waking up to an empty drive, this is the law they have been asking for since the keyless theft crisis began.

What The New Law Actually Says

The Crime and Policing Act 2026 creates two brand new offences under the heading of vehicle theft. The first criminalises the making, adapting, importing or supplying of an electronic device for use in stealing a vehicle or anything inside a vehicle. The second criminalises possession of such a device. Both carry the same maximum sentence: five years’ imprisonment, an unlimited fine, or both.

The Home Office factsheet, published on 11 May, defines an “electronic device” deliberately broadly. It covers signal jammers (which block a key fob from communicating with the car), signal amplifiers and relay devices (which extend the range of a fob so a thief outside the house can wake the car on the drive), and any future tools criminals might invent. The drafters confirmed this was a conscious choice. As the factsheet puts it, “using a broad definition means electronic devices which may be developed in the future would be covered by this legislation.”

The Bill received Royal Assent on 29 April 2026 and the substantive vehicle theft provisions are now in force. Police forces no longer need to wait for a relay attack to take place. They can act the moment one of these devices is found.

Why The Old Law Was Not Working

Before the new Act, possessing a signal jammer was not, in itself, a crime. Offenders could be charged with going equipped to commit theft under section 25 of the Theft Act 1968, or with conspiracy to steal or conspiracy to handle stolen goods. But each of those offences put the burden on the prosecution to prove the offender’s specific intention to steal a vehicle. In practice, that meant a suspect caught with a relay box in their boot could shrug, claim they had found it, and walk away unless the police could tie the device to a planned or completed theft.

The Home Office is open about the failure rate this created. According to the Crime Survey for England and Wales, there were 732,000 incidents of vehicle-related theft in the year to September 2024. Police recorded crime data shows 375,048 vehicle related thefts in the same period, of which 132,412 were theft of a motor vehicle. Police-recorded thefts have surged 21 percent across England and Wales over the last twelve months, and insurers paid out a record £690 million for theft claims alone in 2025.

London tells the sharpest version of the story. The Metropolitan Police Service estimates that electronic devices are used in approximately 60 percent of vehicle thefts across the capital. The Met recorded 16,907 vehicle thefts in 2025 in London alone, which works out at around 46 cars every day. Between 60 and 70 percent of recent stolen cars were keyless models, up from only 14 percent back in 2019. The technology that was supposed to make modern cars more convenient also made them dramatically easier to walk away with.

How A Relay Attack Actually Works

Most modern cars unlock and start by detecting a low-power radio signal from a key fob sitting in the owner’s pocket. That signal is short range by design. The fob and the car only need to “see” each other when the driver is within a couple of metres.

A relay attack defeats this in seconds. One thief stands by the front door of the house holding an amplifier that listens for the signal from the fob inside, often hung on a hook in the hallway. A second thief stands by the car with a paired device. The first device relays the captured signal to the second device, which retransmits it to the car. The car believes the key is right beside it, unlocks, and lets the thief press the start button. By the time the householder realises anything has happened, the car is gone.

The kit needed costs as little as a few hundred pounds online. That is why the Home Office has gone after the supply chain as well as the user. Making, importing or selling these devices now carries the same five-year maximum as possession.

What This Means For Honest Drivers

The most practical upside for ordinary drivers is faster, simpler enforcement. Officers who stop a vehicle and find a signal jammer or relay box in the cabin no longer need to make a case about what the device was about to be used for. The fact of possession, without a credible legitimate explanation, is now the offence. That should mean more seizures, more arrests at the equipment stage, and fewer organised crews able to operate at scale.

The Act is paired with two other powers that matter for vehicle owners. Police can now enter premises without a traditional warrant if a stolen vehicle has been tracked there. And law enforcement can apply to court for a Domain Name Suspension Order or IP Address Suspension Order to take down websites that sell stolen vehicle parts or facilitate organised vehicle crime online.

The Home Office has acknowledged a limited exception for legitimate use. Ofcom-approved signal repeaters, which are used to boost a weak mobile signal indoors, remain legal to own. The factsheet’s frequently asked questions section accepts that “there are very few legitimate uses for these devices” but says anyone with a valid reason for owning one should have no difficulty in demonstrating that.

What To Do If You Are Worried About Theft

The new law does not, on its own, secure your car. Three steps will reduce your risk by an enormous margin. First, keep your key fob away from the front of the house and store it in a Faraday pouch or metal tin overnight. Relay attacks fail if the amplifier outside cannot detect the fob’s signal at all. Second, check whether your car key supports motion sensing, which puts the fob to sleep when it has not moved for thirty seconds, and enable it via the manufacturer’s app or main dealer. Third, fit a Thatcham approved physical defence, such as a steering lock or driveway bollard, because the visible deterrent often sends thieves to the next house.

If your car is stolen, dial 999 immediately and request a crime reference number. Even with the increased police powers under the new Act, the first hour is critical. Notify your insurer the same day, and report the loss to the DVLA at gov.uk/stolen-vehicle. If your car is fitted with a Thatcham category S7 tracker, contact the tracker provider directly so they can begin signal tracing before the vehicle is moved into a container.

For drivers shopping for a new car, the change in the law will also start to filter into insurance pricing. The Association of British Insurers has pushed for criminalisation of these devices for years, arguing that the previous legal vacuum was a major driver of theft claim inflation. Premiums on the most-targeted Range Rovers, Hyundais, Toyota hybrids and Ford Fiestas should ease as theft volumes fall, although the effect will take at least one underwriting cycle to feed through.

What Happens Next

The provisions in the Crime and Policing Act 2026 do not need any further regulations to take effect, so prosecutions can begin immediately. The Home Office is expected to publish guidance for police forces over the summer setting out evidential standards for possession charges, the handling of mixed-use devices like multi-band amplifiers, and the threshold for charging suppliers under the new offences.

The Government has also opened a separate consultation on a wider ban of consumer signal jammers used for shoplifting and tracker disabling, which closed earlier this spring. That additional ban is expected to be brought forward later in 2026 and would extend criminal liability beyond vehicle crime to cover any signal jamming device sold to the public. For drivers, the message from the new Act is simple. The tools have been outlawed. The penalties have been raised. And for the first time, the law is on the side of the person who locked the car on the driveway last night.

Sources:

• Crime and Policing Act 2026: serious crime factsheet (GOV.UK)
• Keyless car theft devices outlawed at last, as police get new powers to track stolen vehicles (Auto Express)
• Keyless car theft devices banned in new law (What Car?)
• Why keyless car theft just got harder in the UK (Regit)
• Crime and Policing Act 2026 (UK Parliament)