Parliamentary Agents are special lawyers who introduce and promote Private Bills through Parliament. As Private Bills affect only a particular group or individual such as a company or a local council it is up to them to petition Parliament to introduce a Bill. The drafting of Private Bills and their conduct through the two Houses is complicated. There are several firms who have satisfied the Speaker with their knowledge of Private Bill procedure and who alone may accept fees for taking a Bill through parliament. Agents must be registered with the Private Bill Office. Parliamentary agents can also act for petitioners opposing a Private Bill.
Further information on this subject can be found from the following link.
Private Bills before Parliament
Private Bills before Parliament: Parliamentary Agents