Many employers are acting like they are in the "Dark Ages" and have "antiquated" views on hiring women, a study has found.
New evidence has found that three in five employers believe it is reasonable to ask a woman if she has young children and if she is pregnant during an interview.
While two in five said women who had more than one child while in the same job could be a "burden" to the team, and half said workers sometimes resented women who were pregnant or on maternity leave.
The Equality and Human Rights Commission (EHRC) said its study revealed antiquated beliefs and showed that many employers needed more support to better understand the basics of discrimination law and the rights of pregnant women and new mothers.
Chief Executive of the Commission, Rebecca Hilsenrath, called the results "a depressing reality".
She continued: "When it comes the rights of pregnant woman and new mothers in the workplace, we are still living in the Dark Ages.
"We should all know very well that it is against the law not to appoint a woman because she is pregnant or might become pregnant.
"Yet we also know women routinely get asked questions around family planning in interviews."
Sarah, a mother of two young children who was made redundant during maternity leave for her first child, said: "It's sad to think that things like this are still happening.
"I feel angry all the time that you can be a mother with young children and unless you're in a job that protects you, your whole world can come tumbling down - out of your control.
"It is essential for employers to be honest and ensure there is good communication between them and those on maternity leave so that pregnant women and new mothers are given the support they deserve."
Campaigners said the results revealed "outdated, discriminatory views" which were holding women back in the workplace.
TUC general secretary Frances O'Grady said that women should not be forced to choose between having a career and a family.
"But thousands are being forced from their job every year. Pregnancy discrimination scars lives and careers.
"Employers are getting away with breaking the law on an industrial scale."
Young Women's Trust chief executive Dr Carole Easton said employers and the economy were both missing out on the talents of young women.
"Today's findings show many employers, given half a chance, would run roughshod over women's rights.
"It's no wonder women are held back in the workplace when people have such outdated, discriminatory views.
"It is employers and our economy that miss out on the talents of young women as a result.
"Young women who want to work are, meanwhile, finding themselves in debt and relying on food banks."
The EHRC wants companies to sign up to its Working Forward initiative, which aims to stamp out pregnancy and maternity discrimination. Member firms are given advice and help to improve in areas such as flexible working and employee confidence.