Monday marked equal pay day - the day where women effectively work for free for the rest of the year thanks to the gender pay gap.
However female apprentices have been working for free since 28 October - two weeks ago.
As well as being paid less, the group is also less likely to receive training and end up with a job than their male counterparts, according to new research from Young Women's Trust and ComRes.
The survey found on average young men are earning 21% more than females while doing an apprenticeship. Females earn just £4.82 an hour compared with £5.85 an hour for males. This means a young woman woman 35 hours a week will be £2,000 worse off over the course of a year.
While undertaking apprenticeships young women are almost twice as likely to report that they missed out on training. Some 7% said they received no training at work (compared to 4% of young men) and 23% received no training outside of work (compared to 12% of young men).
After completing their apprenticeships, some 16% of women found themselves out of work, compared to 6% of men.
As the report points out: "Without training, apprenticeships become a source of cheap labour for employers and offer little benefit to the employee."
Dr Carole Easton, chief executive of Young Women’s Trust, said it was "staggering" certain employment sectors were not welcoming young women.
"Less than 2% of construction apprentices are female and less than 4% of engineering apprentices. And, according to the same official figures, even in IT & Telecoms the figure only rises to 12%."
Easton added: "Apprenticeships often provide young people with a valuable insight into the realities of the workplace and it is incredibly sad that that one of these realities is that many women will be worse off than their male counterparts.
"The gender pay gap isn’t something that opens up later, or exists only in the boardroom.”
The apprentice equal pay day was calculated using the same methodology as the Fawcett Society used to calculate the equal pay day.