More than one in four mothers feel they have been discriminated against at work while pregnant or after returning to their job, according to new research.
A survey of almost 2,000 UK working mothers found that most didn't bother making a formal complaint about unfair treatment.
Half of those polled by law firm Slater & Gordon said they felt left out or not taken seriously at work after having a child, while two out of five believed younger colleagues with no children were given more support and encouragement.
Three out of five said they believed pregnancy was a problem for their workplace and a third found it “impossible” to climb the career ladder after giving birth.
The report said that while the Duchess of Cambridge won't have to worry about the impact of having a child, many women were still facing “archaic” attitudes at work.
Kiran Daurka of Slater & Gordon said: “Despite the equality legislation in place, attitudes and working practices continue to block women in achieving their career aspirations in the UK.
“This report shows that there are still negative perceptions of women with children and this kind of attitude is short-sighted and bad for business.
“Anecdotally, we hear of mothers complaining about being put on a ”mummy track“ when back at work, and this research illustrates that this is a real experience for many women.
“I find it quite dispiriting to hear that more than a fifth of mums feel that they need to prove themselves to their bosses following their return from having baby.”
Employment Minister Jo Swinson commented: “It is illegal to sack a woman because she is pregnant or on maternity leave. Such action constitutes pregnancy discrimination and could result in an employer in front of an employment tribunal.
“The Government is committed to making sure that more businesses make the best use of women's talents throughout the organisation, from boardroom to the shop floor.
“This is why from April 2015 we're introducing shared parental leave and pay which will allow couples to choose how they share care for their child in the first year after birth.”
TUC general secretary Frances O'Grady said: “Every year thousands of women are passed over for promotion, sidelined and even lose their jobs, simply for having children.
“Pregnancy discrimination causes terrible suffering for women and their families. No modern business should prevent staff pursuing their career just because they've become parents, but sadly some employers are still living in the dark ages when it comes to women in the workplace.
“By introducing tribunal fees of up to £1,200 to take an employer to court over pregnancy discrimination, the Government has ensured that many more of these women will have to suffer in silence.”