Youth Work Ireland says it's "wholly unacceptable that young people are paid less for the same work as older people".
The group which works with over 110,000 young people around the country is welcoming the publication of a Sinn Féin Bill which reviews pay discrimination.
The party says workers under 18 are being paid as little as €6.69. which is far below the National Minimum Wage.
Youth Work Ireland says it is fitting that the issue is being highlighted at the same time as the gender pay gap.
Sinn Féin is slamming sub-minimum rates of pay for young people.
The party has published a Bill to scrap the practice by some employers to pay someone as little as 80% of the National Minimum Wage.
It says it is mainly happening to workers in their 20s, simply because it is their first or second year in employment.
Senator Paul Gavan says pay can be far lower than people think.
He said: "There are two rates of pay that are below national minimum wage that people in their first and second year of work experience and also people aged under 18.
"They can be paid as little as €6.69 if they are under 18, or €7.64 or €8.60."