In a study by Stirling University, Professor Andrew Watterson suggested up to 3.5 million shift workers are not visited by HSE – putting their lives at risk.
However, John Osman, the group’s chief medical advisor, said it does perform preventative inspections out-of-hours "where appropriate and necessary".
The representative added that inspections are just one tool used regulate and influence employers – and another "important element" is an assessment of provision for ensuring the health and safety of employees working outside of normal office hours.
"This examination includes a physical inspection of the control measures and consultation with employees and trade unions or safety representatives," he added.
Mr Osman concluded that all concerns regarding shift or out-of-hours working are treated in a serious manner and investigated fully.
HSE said is also carrying out a three-year study of illnesses linked to shift work.
