The Cancer Act 1939 doesn’t make it ‘illegal to cure cancer’

18 August 2026

What was claimed

Under the 1939 Cancer Act it's a criminal offense for medical practitioners to even advise patients on potential cancer cures.

Our verdict

False. The Cancer Act 1939 prohibits advertisements promoting cancer treatments to the general public. It doesn’t prevent medical practitioners from treating patients.

False claims that legislation from 1939 makes it “illegal to cure cancer” are recirculating on Facebook.

Several of the posts claim that “under the 1939 Cancer Act, it's actually a criminal offense for medical practitioners to even advise patients on potential cancer cures”.

Screenshot of social media post with pink "false" text overlaid

This is untrue. The Cancer Act 1939 is a genuine British law, but it doesn’t make it a criminal offence for medical practitioners to advise their patients about potential cures or treatments.

The act does prohibit “certain advertisements relating to cancer”. This includes any kind of advert offering to treat people for cancer, prescribing any kind of remedy for it, or giving advice on how to treat the disease. This ban includes both proven treatments and alternative therapies.

Cancer Research UK describes this part of the act as a “blanket ban on advertising cancer treatments to the general public”. It says the ban is designed to protect cancer patients and the public, and was originally introduced to combat the promotion of unproven remedies at a time when licensed treatments like chemotherapy and radiotherapy were still in their early stages.

Advertisements are allowed, however, if the advertiser can prove it is intended to target MPs, local authorities or medical practitioners rather than patients or the public, because these groups of people are either responsible for treating patients or make decisions about how to use NHS resources.

The ban also doesn’t apply when an advert is published by a local authority, the governing body of a voluntary hospital or anyone acting on “the sanction of the Minister” (meaning the health secretary).

We previously fact checked versions of this claim being shared on social media over a year ago.

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