Worried safety experts have been in touch with the Enquirer to highlight the situation which is spreading across smaller sites in the capital.
Workers are asked to sign a register stating they have had safety induction talks despite no training taking place.
One safety source said: “It has now become common practice on a lot of sites in London for managers to get all workers to sign bogus forms claiming they have been given toolbox safety talks.
“If anyone questions what´s happening they are simply let go because there are plenty of people willing to take their place in the industry at the moment.”
Toolbox talks are seen by the Health and Safety Executive as a highly effective means of spreading the safety message on sites.