Perth politicians in illicit affair

West Australian Greens MP Adele Carles says she had a "stupid" affair with the state's Treasurer Troy Buswell, but it's over and she now deeply regrets it.

Ms Carles, 41, is married with three children while 44-year-old Buswell, who notoriously disgraced himself as an MP by sniffing the chair of a female political staffer, is married with two sons.

Mr Buswell is due to face the media at 1pm today (NZT) after Ms Carles confessed to the "brief" affair in an interview published in a News Limited newspaper.