Rachel Newham from Think Twice, a mental health support group working with young girls, was speaking after it was announced companies with over 250 employees will have to publish their gender pay gap.
£500,000 package aimed at helping the 8,000 employers who will have to publish their average pay and bonus gap between men and women
The first league table will be published in 2018
The Government aims to have 15,000 more girls studying maths and sciences by 2020, a 20% increase on current numbers
Rwanda ranks higher than UK equal pay
She told Premier's News Hour: "Stresses that are going on in terms of work that's piled on them in school and they get to the work place, only to find they've worked really hard and exhausted themselves throughout school, and all of the sudden whatever they do they're not going to get paid as much as a man."
New league tables are also being launched giving details of companies failing to address the problem, and ministers are taking action to make sure that thousands more girls study maths, engineering, science and technology at school.
Women and equalities minister Nicky Morgan said the Government wanted to secure "real equality" for women and reduce the gap in pay between men and women.
Rachel Newham told Premier the pay gap is shocking: "It still staggers me really that men and women are doing the same job and men get paid more than women - it's something we wouldn't like to see still happens in 2016."
Rebecca Hilsenrath, chief executive at the Equality and Human Rights Commission, said: "Today's announcement is a welcome, but long overdue, step in the right direction. Mandatory reporting should encourage large companies to take action to close their gender pay gaps.
"However, while we welcome this requirement for more transparency, we are concerned that the proposals do not appear to provide any sanction for failure to comply. If companies are to take this seriously, we need to be able to use our enforcement powers to ensure that they do what is required."
Listen to Premier's Hannah Tooley speak to Rachel Newham here: