Di Macleod, who is the director of Gold Coast Centre Against Sexual Violence, said that it was not enough to claim that a woman did not say "no".
"Just because a woman says yes to one guy, doesn't mean she consents to his mates watching or taking part as well," the Courier Mail quoted Macleod as saying.
October is Sexual Violence Awareness Month and the centre is focusing its message on the issue of consent by creating two new posters to be distributed to young people.
"It is really important that everyone understands that sex without consent is rape," Macleod said.
"That drunk means no; crying means no; 'I don't want to' means no; asleep means no. In fact only yes means yes," he added.
More than 800 cases of sexual assault were received by the Gold Coast centre last year, and Australian Bureau of Statistics figures reveal that one in five women have experienced sexual violence.
Macleod says that there is anecdotal evidence to show an increase in the number of cases.