The centre has said sexual assaults committed by individuals not known to victims now accounts for more than half of reported cases.
Launching its annual report for 2008, the centre highlighted concern that its funding has been reduced.
It said it accompanied 284 victims of rape and sexual assault to the Sexual Assault Treatment Unit in 2008.
It received over 12,000 calls to its helpline - an increase of 4% on 2007 - however, 25% of these callers either hung up, remained silent, or the call was obscene or a hoax.
Chief Executive Ellen O'Malley Dunlop said she is concerned that rape or sexual assault by a stranger now accounts for 51% of cases reported to them - this represents a 14% increase over a five-year period.
Statistics from the centre also shows that there has been a 20% increase in the number of clients attending for childhood sexual abuse since 2003.
