These are individuals who enter into a contract with an ‘agency’ to undertake work for the agency’s client. The worker provides services to the agency’s client and works under the control of the client.
It is very unlikely that the law will find that the individual is either an employee of the agent, because no control is exercised over the individual, nor of the client since there is no contract between the parties.
Rights relating to agency workers arise under the agency contract. Statutory rights may be afforded to agency workers, such as those arising under the Working Time Regulations.