The Local Authorities (Referendums) (Petitions) (England) Regulations 2011
Under the above Act, a local council must hold a referendum on whether the council should change to a different form of governance if at least 5 per cent of the local government electors in that area petition the local council to do so.
All local councils are required to publish each year the number of electors which corresponds to that 5%, on the basis of the electoral registers for the area as of 15 February each year.