Women typically earn more than men in their 20s, but that the tables are turned as they get older, according to research from the Press Association.
Using data from between 2006 and 2013 from the Office for National Statistics, it says that on average women between the age of 22 and 29 earn £1,111 more than their male counterparts.
However, a man turning 30 in 2006 would have brought in on average £8,775 more than a woman of the same age by 2013.
Ann Pickering, HR director at O2, said the research showed that the gap was due to men being promoted to higher paid jobs in their 30s. Sam Smethers, chief executive of the Fawcett Society, said a big part of the problem was a lack of flexible working in senior roles.
TUC General Secretary Frances O’Grady said: “We all expect our wages to increase as our careers progress. But many women start losing out on well-paid jobs and career opportunities as soon as they get into their thirties.
“Too many employers are stuck in a time warp when it comes to promoting women to senior positions and paying them the going rate. It is shocking that 40 years on from the Equal Pay Act women managers earn 22 per cent less than their male equivalents.
“We will not make a dent in this glass ceiling without a wholesale change in attitudes and practices. We need pay transparency, equal pay audits and a requirement on companies to tackle gender inequality.
“We need a fair labour market that works for everyone and that doesn’t discriminate against women.”