The revocations come after an extensive investigation by CITB, which exposed fraudulent activity in centres where candidates were taking tests accredited by both CITB and the British Safety Council.

This was later broadcast on the BBC Newsnight programme. CSCS wrote to all affected card holders in November 2015, telling them to retake their HS&E test. Vouchers were provided to pay for retesting and steps were taken to reduce inconvenience for businesses.

Graham Wren, CSCS Chief Executive, said: “We take assurance that CITB’s in-depth analysis was accurate. While we accept that some people have been inconvenienced we have kept this to a minimum and removed unsafe cards from circulation.”