The Dublin Rape Crisis Centre (DRCC) said victims of all ages were being affected, including children.
Statistics from the DRCC show that more than 2,000 teenagers under the age of 17 sought counselling last year for rape or sexual assault. This included 1,751 children aged 15 to 17 and 328 under the age of 15.
"There's a disturbing level of violence accompanying rape and sexual violence and it's on the increase," said DRCC chief executive Irene Bergin. She said this has been
reported by counsellors staffing the centre's helpline and volunteers who accompany victims to the sexual assault treatment unit.
DRCC clinical director Angela McCarthy said teenagers under the age of 17 made up a fifth of all genuine counselling helpline calls.
She said the DRCC was constrained both legally and in terms of expertise in providing counselling to teenagers.
"Very often a young person may well be raped, maybe in a context they weren't supposed to be they come home, they shower, get into bed and pull their blankets over their head and say if I don't talk about it, it hasn't happened. That's how they deal with it."
She said the DRCC had liaised with other agencies, including Children at Risk in Ireland (CARI), about providing a service to these teenagers and that a round-table discussion was planned for the autumn.
Ms Bergin highlighted the increasing prevalence of drug-assisted rapes, with
reports to the centre increasing from 0.3% of all calls in 2003 to 1.4% in 2004.
"These figures may not fully reflect the reality of the situation," she said.
"Victims of this type of crime are often reluctant to report to the gardaí or seek help because they fear they may not be believed, as their memories may be unclear."
DRCC chairperson Breda Allen said 4,750 people told the centre in 2004 they were recently raped (in the last 12 months), while official garda figures showed only 447 people reported rape in the entire country last year.
"What those startling figures show is that fewer that 10% of people reported to gardaí and that's just from our figures," she said.
Ms Allen said the real reporting figure could be as low as 2% to 3%.
She said the legal system deprived victims the right to legal representation on the basis it would interfere with the accused's presumption of innocence, enshrined by the Constitution.
She said the DRCC would be pushing this year for a referendum to change the Constitution.