Figures obtained by construction union UCATT revealed a decline in the number of proactive inspections made by the Health and Safety Executive.
A Freedom of Information request revealed that the total number of HSE inspections for 2012/13 was 10,577 compared to 9,656 in 2014/15.
The decline in inspections came at a time when the construction industry was recovering from recession and activity was increasing.
The biggest reduction was in Scotland which saw a drop of 55.7% in inspections.
There were also large decreases in the North East 28.5%, North West 32.5%, the South East 19.6% and in Wales 3.4%.
There were some English regions where the number of inspections increased and the overall reduction for England was 2%.
Brian Rye, Acting General Secretary of UCATT, said: “This fall in inspection activity is deeply troubling.
“The prospect of an unexpected knock on the door by a construction inspector is what keeps many employers on their toes.
“If employers believe that their safety procedures are not going to be checked this will lead to slackness and corners being cut. Workers could pay with their lives.”