Flexible working should be the default position for all employees, rather than it being up to individuals to request.
That is the call from Conservative MP Helen Whately, who introduced a flexible working bill in Parliament on Tuesday.
It would help close the gender pay gap, assist parents to share childcare, and help businesses keep staff, she said.
Anna Whitehouse, founder of the campaign Flex Appeal, said it was “a huge moment”.
Ms Whately’s Ten Minute Rule Bill was given approval to go to a second reading on Wednesday.
Introducing her bill, she argued that unless employers had a sound business reason for having specific working hours, firms should introduce flexibility to every job.
“The 40-hour, five-day working week made sense in an era of single-earner households and stay-at-home mums, but it no longer reflects the reality of how many modern families want to live their lives,” she said.
“At the moment, too many women are reluctantly dropping out of work or going part-time after having children because their employers won’t allow them flexibility.
“This entrenches the assumption that men are the breadwinners and women are the homemakers.
“As a result, men don’t get to spend as much time as they might like with their children, women miss out on career opportunities, and the country loses out on the contribution they could and would like to make – if only they could do slightly different hours or work some days from home.”