There has been a 43% increase in the number of young people reporting rape and sexual assault by teenagers to the CARI helpline over two years.
In its annual report, the helpline reports that it received more than 1,500 calls last year, with most of them coming from mothers. The most common issue reported was abuse within families.
CEO of CARI Mary Flaherty said the majority of calls related to girls under 13.
She said the growth of abuse among teenagers between 2012 and 2014 by their peers was extremely worrying.
"The fact it's amongst friends or gangs would be quite different (from abuse by adults)," she said.
"The nature of the abuse could be anything from assault using violence and coercion. With young people, the internet is becoming a significant factor, where they are initially setting up in relationship and sexting is turning ultimately to actual abuse."
CARI said teenage victims were being “further traumatised” with their assaults being viewed and discussed by peers on social media.
And it said that abused children can wait up to 12 months for therapy because of ongoing funding cuts.
The report said it was “unacceptable” that children who have been abused can be forced to wait up to 12 months for therapy due to cutbacks.