What Is an Agency Worker?
An agency worker has a contract with an agency and is supplied to work under a hirer's supervision. What rights this brings, and when.
An agency worker is someone who is supplied by a temporary work agency to work temporarily for, and under the supervision and direction of, a hirer, and who has a contract with that agency: either a contract of employment or another contract to perform work or services personally. That is the definition in regulation 3 of the Agency Workers Regulations 2010, which apply in England, Wales and Scotland.
Gov.uk puts it more simply: you are an agency worker if you have a contract with an agency but work temporarily for a hirer. You are not one if you use an agency only to find permanent or fixed-term employment (gov.uk: Your rights as an agency worker).
The definition also has an exclusion. Someone is not an agency worker if their contract makes the agency, or the hirer, a client or customer of a profession or business that the individual runs. A genuinely self-employed contractor running their own business can fall outside the regulations on that basis, while a typical temp directed day to day by the hirer is usually within them.
Agency worker rights come in two stages. From the first day of an assignment, an agency worker is entitled to be treated no less favourably than a comparable worker in access to the hirer's collective facilities and amenities, such as a canteen, childcare or transport, unless the hirer can justify the difference on objective grounds (regulation 12). They are also entitled to be told about relevant vacant posts with the hirer (regulation 13).
After 12 continuous calendar weeks in the same role with the same hirer, the agency worker is also entitled to the same basic working and employment conditions, including pay, as they would have had if the hirer had recruited them directly. That qualifying period is explained in the AWR entry, and the AWR 12-week calculator works out the date for a placement.