Is it ok for a non-mahram man to stay (for an extended period) at a house where females of the family reside?

A freind of my father's has recently come from abroad to stay with us. There are women in the house, and for this reason, we (except my father) believe that allowing a ghair mardh to stay is islamically infeasable as it places restrictions upon the women in the house (ie, the need to observe hijab throuhout the duration of his stay in their own home). We have asked my father to put his freind up at a Bed & Breakfast throughout his stay, but he (my father) has thus far declined. My mother is, rightly so I believe, uncomfortable with the present circumstance. I firmly believe that the suitability of this arrangment compromises on the basic islamic principles of purdah. Should my father respect the wishes of the women in the house and politely ask his freind to stay elsewhere? He will be staying for a week.