The website said concealing this information was a “hidden form of discrimination” affecting people returning to work or switching jobs.

Eight out of ten parents and prospective parents surveyed by Mumsnet said they were reluctant to ask potential employers about parental leave policies because they feared it ‘would make a job offer less likely’.

Two thirds said they had found it difficult or impossible to find this information when considering a position.

Last year, 10 large firms including Santander, Deloitte and Accenture, agreed to publish online what they offer parents in terms of leave and pay.

The change was driven by LibDem Deputy Leader Jo Swinson who is calling on the government to require employers of more than 250 people to publish their parental pay and leave policies.

She said: “I am delighted to have Mumsnet support my campaign for employers publishing parental leave and pay policies. This research highlights why transparency on parental pay policies is so vital. Four in five people say they wouldn’t be comfortable asking about parental pay at interview, and my Bill would mean they could find the information without having to ask.

“This is an easy and simple step that all employers can take to create a more supportive culture for new parents. If we are serious about tackling discrimination against new parents and pregnant women, this is one small but important change that is needed.”

Mumsnet founder Justine Roberts said: “This is a hidden form of discrimination that’s gone on for way too long. Women thinking about starting or adding to their families are finding it impossible to make informed judgements about job offers, and dads who want to play their full part are increasingly finding themselves in the same position. They’re in a double-bind, because even asking the question can mean they go no further in an application process.”