I think it's a matter for the Auditor General at the end of the day.
Certainly in Australia we judiciously use footnotes to refer to key sources of evidence, particularly government documents or matters of that kind, and sometimes we use footnotes just to provide a little bit more background information, rather than cluttering up the main report itself. We use a footnote just to provide a little bit more context sometimes, a little bit more background information.
Sheila Fraser is right to say that undue use of that sort of approach does probably cloud the report. So you do have to be careful, and only in significant cases would we use that to help the reader, to provide more context to the reader.