Three out of four part-time workers feel "trapped" in their jobs, with few opportunities for promotion, according to a new study.
Two-thirds believed they would have a chance of promotion only if they increased their working hours, a survey of 1,000 part-time employees by the Timewise Foundation found.
Most of those polled said they downgraded their expectations of pay and level of job when applying for a part-time position.
Karen Mattison, co-founder of the Timewise Foundation, said: "Work in the UK is undergoing a fundamental shift. More than a quarter of UK workers are now part-time or flexible, with most needing to fit their careers with something else in life.
"Yet millions are hitting a wall at key points in their careers, when they want to progress or move to a new role. Doing so, without losing their flexibility, presents a real challenge, leaving many feeling trapped in their current jobs.
"Britain's part-time workers need to know that there are forward-thinking businesses out there that do offer a future where flexibility is no inhibitor to success."