Research by staffing agency Officeteam has found that 66% of office staff are anxious about asking employers for time off to care for their children, despite provisions in the Employment Act 2002. Of the respondents, 50% described themselves as either "anxious" or "very anxious" about approaching their manager.
Parents won the right to apply for flexible working in April when new regulations requiring employers to consider all requests came into force.
However, the poll of 6,000 employees worldwide revealed that 25% of UK office professionals were delaying parenthood for the sake of their career.
Steve Carter, head of Officeteam in the UK, said serious changes were needed in the way managers dealt with parents.
"Today's workplace has put enormous strains on family life and changes clearly need to be made in the way we approach this," he said.
"Employers have to become family friendly by creating an atmosphere where employees are not living in fear about asking for time off to care for children."
He said schemes such as term-time contracts, flexible working plans and a company creche helped build a structured approach to the work/life balance.
Nearly half of UK employees said they would consider not taking a job if they suspected the company was not family friendly, demonstrating that professionals are beginning to put their parenting needs first.
The survey, which was carried out to support the fourth National Parent's Week from 20-26 October, has created a call to action to UK employers and suggested employers must listen to parental needs if they want to offer an attractive place to work.
Similar levels of dissatisfaction were evident in Australia, Germany and France. The French, in particular, seem the most concerned about their jobs, with over half of French workers admitting they have postponed family plans because of fears it would have a negative effect on their career.