The federal Health Department has refused a request for documents setting out how former ministerial staffer Alastair Furnival would avoid a conflict of interest between his business affairs and his role as the chief of staff to the Assistant Health Minister, Fiona Nash.

Mr Furnival resigned from his job on Senator Nash's staff last month, following Fairfax Media revelations about his role in taking down a healthy food rating website and his co-ownership of Australian Public Affairs, a company that had lobbied for the junk-food industry.

"My chief of staff gave a series of undertakings ensuring a strict seperation between the business of APA and himself.": Fiona Nash. Credit:Andrew Meares

Senator Nash told a Senate hearing Mr Furnival had given her a letter setting out how he would manage potential conflicts.

''My chief of staff gave a series of undertakings ensuring a strict separation between the business of APA and himself,'' Senator Nash told the hearing on February 26.