Experts at JSP are warning that the fake hard hats can be split in two with your bare hands.
The British Safety Industry Federation said the counterfeits originated from Asia or the Middle East.
The helmets are copies of JSP’s MkII safety helmet which it has been manufacturing in the UK for over 35 years.
The bogus hard hats are easily identifiable from the marks “Burly” and “MkII” under the peak.
All genuine JSP safety helmets comply with and significantly exceed relevant international performance standards.
Matthew Judson, JSP’s director of technical support, said users should make sure JSP’s name is branded into the helmet, and ensure that the user information leaflet is original – not a photocopy that is not square on the page – correctly spelled, in multiple languages, and with the manufacture’s contact details listed.
They should examine the helmet closely for consistency of colour, clarity and legibility of markings and make sure it is durable.
He said: “If you suspect a helmet is fake, give us a call and we will send someone out to have a look at it, or take it back to the place you bought it from.
“If someone had been wearing a bogus helmet and an object had fallen on their head they could be dead.
“Fakes can kill.”