© Rex Features / David Fisher
Bonham Carter won the accolade for her role as the Queen Mother in The King's Speech, which picked up seven awards altogether.
Collecting the award, Bonham Carter said that there was "no doubt that, were [her] father alive, he would have given this to her [mother]".
Afterwards she added: "My dad [Raymond] was really disabled for the last 25 years of his life and mum was really extraordinary in tireless caretaking, and also looking for anything that would help him suffer less.
"She so genuinely qualified to be 'Best Supporting Wife'."
