We would advise you gather as much information as possible, such as the type of rubbish being left, where and when it was left and then contact your local authority (normally the Environmental Protection Department).
If the amount being left is a very large quantity then you should report the matter to the Environment Agency National Customer Contact Centre (NCCC): 03708 506 506.
We would also advise you to contact the police in these circumstances with as much information as possible, including descriptions of the people, vehicles involved and registration numbers, because in extreme cases the police can take action, although they may decide to work with the local authority Environmental Protection Department.
See the website in Related Information to find your local authority's contact information.