An individual or business that provides workers for agricultural work is called a ‘gangmaster’.
Gangmasters must be licensed if they provide workers for:
agriculture
horticulture
dairy farming
food and drink processing or packaging
forestry
gathering shellfish (anybody who uses supplied workers to gather shellfish also needs to be licensed)
There are some jobs in these industries that do not need a gangmaster licence.
You can check if a gangmaster is licensed.