what exactly does it mean by drawing an adverse inference and how does it work in terms of decision making.

any help would be greatly appreciated as i am very inexperienced in the Housing benefit realm.

Cheers.

As good a starting point as any is R(H) 3/05.
www.administrativeappeals.tribunals.gov.uk/aspx/view.aspx?id=1475

In summary, the "inference" approach is typically taken where evidence / information is not provided, or is incomplete, or is unavailable. However, any inference that is drawn must (normally) be with regard to any relevant evidence / information that is already available.