Which of the following is likely to issue an improvement notice?

An improvement notice is a formal notification issued typically by an authoritative body in response to health and safety concerns in the workplace. The organization most equipped to issue such notices is the Health and Safety Executive (HSE). This agency is responsible for ensuring compliance with health and safety regulations across various industries in the UK. When there are systematic breaches of health and safety laws or when work practices could lead to risk, the HSE can intervene by issuing an improvement notice.

The improvement notice serves as a legal order requiring the recipient to make specified changes or improvements within a set timeframe, thereby helping to mitigate risks and protect workers. The authority embedded within the HSE ensures that they have the requisite expertise and statutory backing to enforce such notices, underlining their role as a regulatory body.

The other choices, such as a main contractor, sub-contractor, or site manager, do play essential roles in site management and safety, but they do not possess the same level of authority to formally issue improvement notices. They can, however, be involved in identifying safety concerns that might lead to notices being required, but the actual issuing is reserved for the relevant regulatory body like the HSE.