Most Government publications are only published online, so you would be expected to include the web address in your reference.
In Harvard (Cite Them Right), many Government reports/publications will end up looking like a standard 'webpage' reference:
Author (year of publication) Title of document. Available at: URL (Accessed: date).
You should be able to adapt this to suit other referencing styles. The author may be a specific person, or it may be the Government department, usually listed on the front page e.g. Department for Education; HM Government etc.
For more examples please see Cite Them Right Online - Governmental. (This includes examples where there is a 'command number' or Cm number, such as Green and White Papers).
